typo

memtop cx16
refresh compiled examples
2026-10-23 12:02:29 +00:00 · 2020-09-23 18:50:32 +02:00 · 2020-09-23 02:34:49 +02:00 · 2020-09-23 00:29:40 +02:00 · 2020-09-23 00:22:36 +02:00 · 2020-09-22 23:22:20 +02:00
196 changed files with 18958 additions and 20769 deletions
@@ -14,7 +14,7 @@ docs/build
 out/
 parser/**/*.interp
 parser/**/*.tokens
-
+parser/**/*.java
 *.py[cod]
 *.egg
 *.egg-info
@@ -4,8 +4,8 @@ sudo: false
 # dist: xenial

 before_install:
-  - chmod +x gradlew
+  - chmod +x ./gradlew

 script:
-  - gradle test
+  - ./gradlew test

@@ -1,23 +1,33 @@
 [![saythanks](https://img.shields.io/badge/say-thanks-ff69b4.svg)](https://saythanks.io/to/irmen)
 [![Build Status](https://travis-ci.org/irmen/prog8.svg?branch=master)](https://travis-ci.org/irmen/prog8)
+[![Documentation](https://readthedocs.org/projects/prog8/badge/?version=latest)](https://prog8.readthedocs.io/)

-Prog8 - Structured Programming Language for 8-bit 6502/6510 microprocessors
-===========================================================================
+Prog8 - Structured Programming Language for 8-bit 6502/65c02 microprocessors
+============================================================================

 *Written by Irmen de Jong (irmen@razorvine.net)*

 *Software license: GNU GPL 3.0, see file LICENSE*


-This is a structured programming language for the 8-bit 6502/6510 microprocessor from the late 1970's and 1980's
+This is a structured programming language for the 8-bit 6502/6510/65c02 microprocessor from the late 1970's and 1980's
 as used in many home computers from that era. It is a medium to low level programming language,
-which aims to provide many conveniences over raw assembly code (even when using a macro assembler):
+which aims to provide many conveniences over raw assembly code (even when using a macro assembler).

- reduction of source code length
+Documentation
+-------------
+Full documentation (syntax reference, how to use the language and the compiler, etc.) can be found at:
+https://prog8.readthedocs.io/
+
+
+What use Prog8 provide?
+-----------------------
+
+- reduction of source code length over raw assembly
 - modularity, symbol scoping, subroutines
 - various data types other than just bytes (16-bit words, floats, strings)
 - automatic variable allocations, automatic string and array variables and string sharing
- subroutines with a input- and output parameter signature
+- subroutines with an input- and output parameter signature
 - constant folding in expressions
 - conditional branches
 - 'when' statement to provide a concise jump table alternative to if/elseif chains
@@ -28,25 +38,24 @@ which aims to provide many conveniences over raw assembly code (even when using
 - inline assembly allows you to have full control when every cycle or byte matters
 - many built-in functions such as ``sin``, ``cos``, ``rnd``, ``abs``, ``min``, ``max``, ``sqrt``, ``msb``, ``rol``, ``ror``, ``swap``, ``memset``, ``memcopy``, ``sort`` and ``reverse``

-Rapid edit-compile-run-debug cycle:
+*Rapid edit-compile-run-debug cycle:*

- use modern PC to work on
- quick compilation times (seconds)
- option to automatically run the program in the Vice emulator
+- use a modern PC to do the work on
+- very quick compilation times
+- can automatically run the program in the Vice emulator after succesful compilation
 - breakpoints, that let the Vice emulator drop into the monitor if execution hits them
 - source code labels automatically loaded in Vice emulator so it can show them in disassembly
- virtual machine that can execute compiled code directy on the host system,
-  without having to actually convert it to assembly to run on a real 6502

-It is mainly targeted at the Commodore-64 machine at this time.
-Contributions to add support for other 8-bit (or other?!) machines are welcome.
+*Two supported compiler targets* (contributions to improve these or to add support for other machines are welcome!):

-Documentation/manual
--------------------
-This describes the language, but also how to build and run the compiler. See https://prog8.readthedocs.io/
+- "c64": Commodore-64  (6510 CPU = almost a 6502)  premium support.
+- "cx16": [CommanderX16](https://www.commanderx16.com)  (65c02 CPU)  experimental support.
+- If you only use standard kernel and prog8 library routines, it is possible to compile the *exact same program* for both machines (just change the compiler target flag)!

-Required tools
--------------
+
+
+Additional required tools
+-------------------------

 [64tass](https://sourceforge.net/projects/tass64/) - cross assembler. Install this on your shell path.
 A recent .exe version of this tool for Windows can be obtained from my [clone](https://github.com/irmen/64tass/releases) of this project.
@@ -56,8 +65,9 @@ A **Java runtime (jre or jdk), version 8 or newer**  is required to run a prepac
 If you want to build it from source, you'll need a Java SDK + Kotlin 1.3.x SDK (or for instance,
 IntelliJ IDEA with the Kotlin plugin).

-It's handy to have a C-64 emulator or a real C-64 to run the programs on. The compiler assumes the presence
-of the [Vice emulator](http://vice-emu.sourceforge.net/)
+It's handy to have an emulator (or a real machine perhaps!) to run the programs on. The compiler assumes the presence
+of the [Vice emulator](http://vice-emu.sourceforge.net/)  for the C64 target,
+and the [x16emu emulator](https://github.com/commanderx16/x16-emulator) for the CommanderX16 target.


 Example code
@@ -65,44 +75,45 @@ Example code

 This code calculates prime numbers using the Sieve of Eratosthenes algorithm::

-    %import c64utils
+    %import textio
    %zeropage basicsafe
-
+    
    main {
-
+    
        ubyte[256] sieve
-        ubyte candidate_prime = 2
-
+        ubyte candidate_prime = 2       ; is increased in the loop
+    
        sub start() {
-            memset(sieve, 256, false)
-
-            c64scr.print("prime numbers up to 255:\n\n")
+            ; clear the sieve, to reset starting situation on subsequent runs
+            memset(sieve, 256, false)   
+            ; calculate primes
+            txt.print("prime numbers up to 255:\n\n")
            ubyte amount=0
-            while true {
+            repeat {
                ubyte prime = find_next_prime()
                if prime==0
                    break
-                c64scr.print_ub(prime)
-                c64scr.print(", ")
+                txt.print_ub(prime)
+                txt.print(", ")
                amount++
            }
-            c64.CHROUT('\n')
-            c64scr.print("number of primes (expected 54): ")
-            c64scr.print_ub(amount)
-            c64.CHROUT('\n')
+            txt.chrout('\n')
+            txt.print("number of primes (expected 54): ")
+            txt.print_ub(amount)
+            txt.chrout('\n')
        }
-
-
+    
        sub find_next_prime() -> ubyte {
-
            while sieve[candidate_prime] {
                candidate_prime++
                if candidate_prime==0
-                    return 0
+                    return 0        ; we wrapped; no more primes available in the sieve
            }
-
+    
+            ; found next one, mark the multiples and return it.
            sieve[candidate_prime] = true
            uword multiple = candidate_prime
+    
            while multiple < len(sieve) {
                sieve[lsb(multiple)] = true
                multiple += candidate_prime
@@ -112,11 +123,11 @@ This code calculates prime numbers using the Sieve of Eratosthenes algorithm::
    }


+
 when compiled an ran on a C-64 you'll get:

 ![c64 screen](docs/source/_static/primes_example.png)

-
 One of the included examples (wizzine.p8) animates a bunch of sprite balloons and looks like this:

 ![wizzine screen](docs/source/_static/wizzine.png)
@@ -128,3 +139,8 @@ Another example (cube3d-sprites.p8) draws the vertices of a rotating 3d cube:
 If you want to play a video game, a fully working Tetris clone is included in the examples:

 ![tehtriz_screen](docs/source/_static/tehtriz.png)
+
+The CommanderX16 compiler target is quite capable already too, here's a well known space ship 
+animated in 3D with hidden line removal, in the CommanderX16 emulator:
+
+![cobra3d](docs/source/_static/cobra3d.png)
@@ -1,11 +1,11 @@
 buildscript {
    dependencies {
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.3.70"
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.4.10"
    }
 }

 plugins {
-    // id "org.jetbrains.kotlin.jvm" version "1.3.70"
+    // id "org.jetbrains.kotlin.jvm" version "1.4.10"
    id 'application'
    id 'org.jetbrains.dokka' version "0.9.18"
    id 'com.github.johnrengelman.shadow' version '5.2.0'
@@ -110,3 +110,7 @@ dokka {
    outputFormat = 'html'
    outputDirectory = "$buildDir/kdoc"
 }
+
+task wrapper(type: Wrapper) {
+    gradleVersion = '6.1.1'
+}
@@ -1,49 +1,56 @@
 ; --- low level floating point assembly routines for the C64

+FL_ONE_const	.byte  129     			; 1.0
+FL_ZERO_const	.byte  0,0,0,0,0		; 0.0
+
+floats_store_reg	.byte  0		; temp storage
+
+
 ub2float	.proc
 		; -- convert ubyte in SCRATCH_ZPB1 to float at address A/Y
 		;    clobbers A, Y
-		stx  c64.SCRATCH_ZPREGX
-		sta  c64.SCRATCH_ZPWORD2
-		sty  c64.SCRATCH_ZPWORD2+1
-		ldy  c64.SCRATCH_ZPB1
-		jsr  FREADUY
-_fac_to_mem	ldx  c64.SCRATCH_ZPWORD2
-		ldy  c64.SCRATCH_ZPWORD2+1
+		stx  P8ZP_SCRATCH_REG
+		sta  P8ZP_SCRATCH_W2
+		sty  P8ZP_SCRATCH_W2+1
+		ldy  P8ZP_SCRATCH_B1
+		lda  #0
+		jsr  GIVAYF
+_fac_to_mem	ldx  P8ZP_SCRATCH_W2
+		ldy  P8ZP_SCRATCH_W2+1
 		jsr  MOVMF
-		ldx  c64.SCRATCH_ZPREGX
+		ldx  P8ZP_SCRATCH_REG
 		rts
 		.pend

 b2float		.proc
 		; -- convert byte in SCRATCH_ZPB1 to float at address A/Y
 		;    clobbers A, Y
-		stx  c64.SCRATCH_ZPREGX
-		sta  c64.SCRATCH_ZPWORD2
-		sty  c64.SCRATCH_ZPWORD2+1
-		lda  c64.SCRATCH_ZPB1
+		stx  P8ZP_SCRATCH_REG
+		sta  P8ZP_SCRATCH_W2
+		sty  P8ZP_SCRATCH_W2+1
+		lda  P8ZP_SCRATCH_B1
 		jsr  FREADSA
 		jmp  ub2float._fac_to_mem
 		.pend

 uw2float	.proc
 		; -- convert uword in SCRATCH_ZPWORD1 to float at address A/Y
-		stx  c64.SCRATCH_ZPREGX
-		sta  c64.SCRATCH_ZPWORD2
-		sty  c64.SCRATCH_ZPWORD2+1
-		lda  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
+		stx  P8ZP_SCRATCH_REG
+		sta  P8ZP_SCRATCH_W2
+		sty  P8ZP_SCRATCH_W2+1
+		lda  P8ZP_SCRATCH_W1
+		ldy  P8ZP_SCRATCH_W1+1
 		jsr  GIVUAYFAY
 		jmp  ub2float._fac_to_mem
 		.pend

 w2float		.proc
 		; -- convert word in SCRATCH_ZPWORD1 to float at address A/Y
-		stx  c64.SCRATCH_ZPREGX
-		sta  c64.SCRATCH_ZPWORD2
-		sty  c64.SCRATCH_ZPWORD2+1
-		ldy  c64.SCRATCH_ZPWORD1
-		lda  c64.SCRATCH_ZPWORD1+1
+		stx  P8ZP_SCRATCH_REG
+		sta  P8ZP_SCRATCH_W2
+		sty  P8ZP_SCRATCH_W2+1
+		ldy  P8ZP_SCRATCH_W1
+		lda  P8ZP_SCRATCH_W1+1
 		jsr  GIVAYF
 		jmp  ub2float._fac_to_mem
 		.pend
@@ -51,8 +58,8 @@ w2float		.proc
 stack_b2float	.proc
 		; -- b2float operating on the stack
 		inx
-		lda  c64.ESTACK_LO,x
-		stx  c64.SCRATCH_ZPREGX
+		lda  P8ESTACK_LO,x
+		stx  P8ZP_SCRATCH_REG
 		jsr  FREADSA
 		jmp  push_fac1_as_result
 		.pend
@@ -60,9 +67,9 @@ stack_b2float	.proc
 stack_w2float	.proc
 		; -- w2float operating on the stack
 		inx
-		ldy  c64.ESTACK_LO,x
-		lda  c64.ESTACK_HI,x
-		stx  c64.SCRATCH_ZPREGX
+		ldy  P8ESTACK_LO,x
+		lda  P8ESTACK_HI,x
+		stx  P8ZP_SCRATCH_REG
 		jsr  GIVAYF
 		jmp  push_fac1_as_result
 		.pend
@@ -70,44 +77,45 @@ stack_w2float	.proc
 stack_ub2float	.proc
 		; -- ub2float operating on the stack
 		inx
-		lda  c64.ESTACK_LO,x
-		stx  c64.SCRATCH_ZPREGX
+		lda  P8ESTACK_LO,x
+		stx  P8ZP_SCRATCH_REG
 		tay
-		jsr  FREADUY
+		lda  #0
+		jsr  GIVAYF
 		jmp  push_fac1_as_result
 		.pend

 stack_uw2float	.proc
 		; -- uw2float operating on the stack
 		inx
-		lda  c64.ESTACK_LO,x
-		ldy  c64.ESTACK_HI,x
-		stx  c64.SCRATCH_ZPREGX
+		lda  P8ESTACK_LO,x
+		ldy  P8ESTACK_HI,x
+		stx  P8ZP_SCRATCH_REG
 		jsr  GIVUAYFAY
 		jmp  push_fac1_as_result
 		.pend

 stack_float2w	.proc               ; also used for float2b
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  AYINT
-		ldx  c64.SCRATCH_ZPREGX
+		ldx  P8ZP_SCRATCH_REG
 		lda  $64
-		sta  c64.ESTACK_HI,x
+		sta  P8ESTACK_HI,x
 		lda  $65
-		sta  c64.ESTACK_LO,x
+		sta  P8ESTACK_LO,x
 		dex
 		rts
 		.pend

 stack_float2uw	.proc               ; also used for float2ub
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  GETADR
-		ldx  c64.SCRATCH_ZPREGX
-		sta  c64.ESTACK_HI,x
+		ldx  P8ZP_SCRATCH_REG
+		sta  P8ESTACK_HI,x
 		tya
-		sta  c64.ESTACK_LO,x
+		sta  P8ESTACK_LO,x
 		dex
 		rts
 		.pend
@@ -115,79 +123,68 @@ stack_float2uw	.proc               ; also used for float2ub
 push_float	.proc
 		; ---- push mflpt5 in A/Y onto stack
 		; (taking 3 stack positions = 6 bytes of which 1 is padding)
-		sta  c64.SCRATCH_ZPWORD1
-		sty  c64.SCRATCH_ZPWORD1+1
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
 		ldy  #0
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  c64.ESTACK_LO,x
+		lda  (P8ZP_SCRATCH_W1),y
+		sta  P8ESTACK_LO,x
 		iny
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  c64.ESTACK_HI,x
+		lda  (P8ZP_SCRATCH_W1),y
+		sta  P8ESTACK_HI,x
 		dex
 		iny
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  c64.ESTACK_LO,x
+		lda  (P8ZP_SCRATCH_W1),y
+		sta  P8ESTACK_LO,x
 		iny
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  c64.ESTACK_HI,x
+		lda  (P8ZP_SCRATCH_W1),y
+		sta  P8ESTACK_HI,x
 		dex
 		iny
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  c64.ESTACK_LO,x
+		lda  (P8ZP_SCRATCH_W1),y
+		sta  P8ESTACK_LO,x
 		dex
 		rts
 		.pend

 func_rndf	.proc
 		; -- put a random floating point value on the stack
-		stx  c64.SCRATCH_ZPREG
+		stx  P8ZP_SCRATCH_REG
 		lda  #1
 		jsr  FREADSA
 		jsr  RND		; rng into fac1
 		ldx  #<_rndf_rnum5
 		ldy  #>_rndf_rnum5
 		jsr  MOVMF	; fac1 to mem X/Y
-		ldx  c64.SCRATCH_ZPREG
+		ldx  P8ZP_SCRATCH_REG
 		lda  #<_rndf_rnum5
 		ldy  #>_rndf_rnum5
 		jmp  push_float
 _rndf_rnum5	.byte  0,0,0,0,0
 		.pend

-push_float_from_indexed_var	.proc
-		; -- push the float from the array at A/Y with index on stack, onto the stack.
-		sta  c64.SCRATCH_ZPWORD1
-		sty  c64.SCRATCH_ZPWORD1+1
-		jsr  prog8_lib.pop_index_times_5
-		jsr  prog8_lib.add_a_to_zpword
-		lda  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
-		jmp  push_float
-		.pend
-
 pop_float	.proc
 		; ---- pops mflpt5 from stack to memory A/Y
 		; (frees 3 stack positions = 6 bytes of which 1 is padding)
-		sta  c64.SCRATCH_ZPWORD1
-		sty  c64.SCRATCH_ZPWORD1+1
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
 		ldy  #4
 		inx
-		lda  c64.ESTACK_LO,x
-		sta  (c64.SCRATCH_ZPWORD1),y
+		lda  P8ESTACK_LO,x
+		sta  (P8ZP_SCRATCH_W1),y
 		dey
 		inx
-		lda  c64.ESTACK_HI,x
-		sta  (c64.SCRATCH_ZPWORD1),y
+		lda  P8ESTACK_HI,x
+		sta  (P8ZP_SCRATCH_W1),y
 		dey
-		lda  c64.ESTACK_LO,x
-		sta  (c64.SCRATCH_ZPWORD1),y
+		lda  P8ESTACK_LO,x
+		sta  (P8ZP_SCRATCH_W1),y
 		dey
 		inx
-		lda  c64.ESTACK_HI,x
-		sta  (c64.SCRATCH_ZPWORD1),y
+		lda  P8ESTACK_HI,x
+		sta  (P8ZP_SCRATCH_W1),y
 		dey
-		lda  c64.ESTACK_LO,x
-		sta  (c64.SCRATCH_ZPWORD1),y
+		lda  P8ESTACK_LO,x
+		sta  (P8ZP_SCRATCH_W1),y
 		rts
 		.pend

@@ -201,110 +198,74 @@ pop_float_fac1	.proc
 		jmp  MOVFM
 		.pend

+pop_float_fac2	.proc
+		; -- pops float from stack into FAC2
+		lda  #<fmath_float1
+		ldy  #>fmath_float1
+		jsr  pop_float
+		lda  #<fmath_float1
+		ldy  #>fmath_float1
+		jmp  CONUPK
+		.pend
+
 pop_float_to_indexed_var	.proc
 		; -- pop the float on the stack, to the memory in the array at A/Y indexed by the byte on stack
-		sta  c64.SCRATCH_ZPWORD1
-		sty  c64.SCRATCH_ZPWORD1+1
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
 		jsr  prog8_lib.pop_index_times_5
 		jsr  prog8_lib.add_a_to_zpword
-		lda  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
+		lda  P8ZP_SCRATCH_W1
+		ldy  P8ZP_SCRATCH_W1+1
 		jmp  pop_float
 		.pend

 copy_float	.proc
 		; -- copies the 5 bytes of the mflt value pointed to by SCRATCH_ZPWORD1,
 		;    into the 5 bytes pointed to by A/Y.  Clobbers A,Y.
-		sta  c64.SCRATCH_ZPWORD2
-		sty  c64.SCRATCH_ZPWORD2+1
-		ldy  #0
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  (c64.SCRATCH_ZPWORD2),y
-		iny
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  (c64.SCRATCH_ZPWORD2),y
-		iny
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  (c64.SCRATCH_ZPWORD2),y
-		iny
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  (c64.SCRATCH_ZPWORD2),y
-		iny
-		lda  (c64.SCRATCH_ZPWORD1),y
-		sta  (c64.SCRATCH_ZPWORD2),y
+		sta  _target+1
+		sty  _target+2
+		ldy  #4
+_loop		lda  (P8ZP_SCRATCH_W1),y
+_target		sta  $ffff,y			; modified
+		dey
+		bpl  _loop
 		rts
 		.pend

 inc_var_f	.proc
 		; -- add 1 to float pointed to by A/Y
-		sta  c64.SCRATCH_ZPWORD1
-		sty  c64.SCRATCH_ZPWORD1+1
-		stx  c64.SCRATCH_ZPREGX
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		stx  P8ZP_SCRATCH_REG
 		jsr  MOVFM
-		lda  #<FL_FONE
-		ldy  #>FL_FONE
+		lda  #<FL_ONE_const
+		ldy  #>FL_ONE_const
 		jsr  FADD
-		ldx  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
+		ldx  P8ZP_SCRATCH_W1
+		ldy  P8ZP_SCRATCH_W1+1
 		jsr  MOVMF
-		ldx  c64.SCRATCH_ZPREGX
+		ldx  P8ZP_SCRATCH_REG
 		rts
 		.pend

 dec_var_f	.proc
 		; -- subtract 1 from float pointed to by A/Y
-		sta  c64.SCRATCH_ZPWORD1
-		sty  c64.SCRATCH_ZPWORD1+1
-		stx  c64.SCRATCH_ZPREGX
-		lda  #<FL_FONE
-		ldy  #>FL_FONE
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		stx  P8ZP_SCRATCH_REG
+		lda  #<FL_ONE_const
+		ldy  #>FL_ONE_const
 		jsr  MOVFM
-		lda  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
+		lda  P8ZP_SCRATCH_W1
+		ldy  P8ZP_SCRATCH_W1+1
 		jsr  FSUB
-		ldx  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
+		ldx  P8ZP_SCRATCH_W1
+		ldy  P8ZP_SCRATCH_W1+1
 		jsr  MOVMF
-		ldx  c64.SCRATCH_ZPREGX
+		ldx  P8ZP_SCRATCH_REG
 		rts
 		.pend

-inc_indexed_var_f	.proc
-		; -- add 1 to float in array pointed to by A/Y, at index X
-		pha
-		txa
-		sta  c64.SCRATCH_ZPB1
-		asl  a
-		asl  a
-		clc
-		adc  c64.SCRATCH_ZPB1
-		sta  c64.SCRATCH_ZPB1
-		pla
-		clc
-		adc  c64.SCRATCH_ZPB1
-		bcc  +
-		iny
-+		jmp  inc_var_f
-		.pend
-
-dec_indexed_var_f	.proc
-		; -- subtract 1 to float in array pointed to by A/Y, at index X
-		pha
-		txa
-		sta  c64.SCRATCH_ZPB1
-		asl  a
-		asl  a
-		clc
-		adc  c64.SCRATCH_ZPB1
-		sta  c64.SCRATCH_ZPB1
-		pla
-		clc
-		adc  c64.SCRATCH_ZPB1
-		bcc  +
-		iny
-+		jmp  dec_var_f
-		.pend
-

 pop_2_floats_f2_in_fac1	.proc
 		; -- pop 2 floats from stack, load the second one in FAC1 as well
@@ -330,7 +291,7 @@ push_fac1_as_result	.proc
 		jsr  MOVMF
 		lda  #<fmath_float1
 		ldy  #>fmath_float1
-		ldx  c64.SCRATCH_ZPREGX
+		ldx  P8ZP_SCRATCH_REG
 		jmp  push_float
 		.pend

@@ -342,21 +303,21 @@ pow_f		.proc
 		lda  #<fmath_float1
 		ldy  #>fmath_float1
 		jsr  pop_float
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		lda  #<fmath_float1
 		ldy  #>fmath_float1
 		jsr  CONUPK		; fac2 = float1
 		lda  #<fmath_float2
 		ldy  #>fmath_float2
 		jsr  FPWR
-		ldx  c64.SCRATCH_ZPREGX
+		ldx  P8ZP_SCRATCH_REG
 		jmp  push_fac1_as_result
 		.pend

 div_f		.proc
 		; -- push f1/f2 on stack
 		jsr  pop_2_floats_f2_in_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		lda  #<fmath_float1
 		ldy  #>fmath_float1
 		jsr  FDIV
@@ -366,7 +327,7 @@ div_f		.proc
 add_f		.proc
 		; -- push f1+f2 on stack
 		jsr  pop_2_floats_f2_in_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		lda  #<fmath_float1
 		ldy  #>fmath_float1
 		jsr  FADD
@@ -376,7 +337,7 @@ add_f		.proc
 sub_f		.proc
 		; -- push f1-f2 on stack
 		jsr  pop_2_floats_f2_in_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		lda  #<fmath_float1
 		ldy  #>fmath_float1
 		jsr  FSUB
@@ -386,7 +347,7 @@ sub_f		.proc
 mul_f		.proc
 		; -- push f1*f2 on stack
 		jsr  pop_2_floats_f2_in_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		lda  #<fmath_float1
 		ldy  #>fmath_float1
 		jsr  FMULT
@@ -396,7 +357,7 @@ mul_f		.proc
 neg_f		.proc
 		; -- push -flt back on stack
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  NEGOP
 		jmp  push_fac1_as_result
 		.pend
@@ -404,7 +365,7 @@ neg_f		.proc
 abs_f		.proc
 		; -- push abs(float) on stack (as float)
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  ABS
 		jmp  push_fac1_as_result
 		.pend
@@ -415,24 +376,24 @@ equal_f		.proc
 		inx
 		inx
 		inx
-		lda  c64.ESTACK_LO-3,x
-		cmp  c64.ESTACK_LO,x
+		lda  P8ESTACK_LO-3,x
+		cmp  P8ESTACK_LO,x
 		bne  _equals_false
-		lda  c64.ESTACK_LO-2,x
-		cmp  c64.ESTACK_LO+1,x
+		lda  P8ESTACK_LO-2,x
+		cmp  P8ESTACK_LO+1,x
 		bne  _equals_false
-		lda  c64.ESTACK_LO-1,x
-		cmp  c64.ESTACK_LO+2,x
+		lda  P8ESTACK_LO-1,x
+		cmp  P8ESTACK_LO+2,x
 		bne  _equals_false
-		lda  c64.ESTACK_HI-2,x
-		cmp  c64.ESTACK_HI+1,x
+		lda  P8ESTACK_HI-2,x
+		cmp  P8ESTACK_HI+1,x
 		bne  _equals_false
-		lda  c64.ESTACK_HI-1,x
-		cmp  c64.ESTACK_HI+2,x
+		lda  P8ESTACK_HI-1,x
+		cmp  P8ESTACK_HI+2,x
 		bne  _equals_false
 _equals_true	lda  #1
 _equals_store	inx
-		sta  c64.ESTACK_LO+1,x
+		sta  P8ESTACK_LO+1,x
 		rts
 _equals_false	lda  #0
 		beq  _equals_store
@@ -442,7 +403,7 @@ notequal_f	.proc
 		; -- are the two mflpt5 numbers on the stack different?
 		jsr  equal_f
 		eor  #1		; invert the result
-		sta  c64.ESTACK_LO+1,x
+		sta  P8ESTACK_LO+1,x
 		rts
 		.pend

@@ -495,12 +456,12 @@ compare_floats	.proc
 		jsr  MOVFM		; fac1 = flt1
 		lda  #<fmath_float2
 		ldy  #>fmath_float2
-		stx  c64.SCRATCH_ZPREG
+		stx  P8ZP_SCRATCH_REG
 		jsr  FCOMP		; A = flt1 compared with flt2 (0=equal, 1=flt1>flt2, 255=flt1<flt2)
-		ldx  c64.SCRATCH_ZPREG
+		ldx  P8ZP_SCRATCH_REG
 		rts
 _return_false	lda  #0
-_return_result  sta  c64.ESTACK_LO,x
+_return_result  sta  P8ESTACK_LO,x
 		dex
 		rts
 _return_true	lda  #1
@@ -510,7 +471,7 @@ _return_true	lda  #1
 func_sin	.proc
 		; -- push sin(f) back onto stack
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  SIN
 		jmp  push_fac1_as_result
 		.pend
@@ -518,7 +479,7 @@ func_sin	.proc
 func_cos	.proc
 		; -- push cos(f) back onto stack
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  COS
 		jmp  push_fac1_as_result
 		.pend
@@ -526,7 +487,7 @@ func_cos	.proc
 func_tan	.proc
 		; -- push tan(f) back onto stack
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  TAN
 		jmp  push_fac1_as_result
 		.pend
@@ -534,7 +495,7 @@ func_tan	.proc
 func_atan	.proc
 		; -- push atan(f) back onto stack
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  ATN
 		jmp  push_fac1_as_result
 		.pend
@@ -542,7 +503,7 @@ func_atan	.proc
 func_ln		.proc
 		; -- push ln(f) back onto stack
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  LOG
 		jmp  push_fac1_as_result
 		.pend
@@ -550,7 +511,7 @@ func_ln		.proc
 func_log2	.proc
 		; -- push log base 2, ln(f)/ln(2), back onto stack
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  LOG
 		jsr  MOVEF
 		lda  #<c64.FL_LOG2
@@ -562,7 +523,7 @@ func_log2	.proc

 func_sqrt	.proc
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  SQR
 		jmp  push_fac1_as_result
 		.pend
@@ -570,7 +531,7 @@ func_sqrt	.proc
 func_rad	.proc
 		; -- convert degrees to radians (d * pi / 180)
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		lda  #<_pi_div_180
 		ldy  #>_pi_div_180
 		jsr  FMULT
@@ -581,7 +542,7 @@ _pi_div_180	.byte 123, 14, 250, 53, 18		; pi / 180
 func_deg	.proc
 		; -- convert radians to degrees (d * (1/ pi * 180))
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		lda  #<_one_over_pi_div_180
 		ldy  #>_one_over_pi_div_180
 		jsr  FMULT
@@ -591,7 +552,7 @@ _one_over_pi_div_180	.byte 134, 101, 46, 224, 211		; 1 / (pi * 180)

 func_round	.proc
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  FADDH
 		jsr  INT
 		jmp  push_fac1_as_result
@@ -599,7 +560,7 @@ func_round	.proc

 func_floor	.proc
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		jsr  INT
 		jmp  push_fac1_as_result
 		.pend
@@ -607,7 +568,7 @@ func_floor	.proc
 func_ceil	.proc
 		; -- ceil: tr = int(f); if tr==f -> return  else return tr+1
 		jsr  pop_float_fac1
-		stx  c64.SCRATCH_ZPREGX
+		stx  P8ZP_SCRATCH_REG
 		ldx  #<fmath_float1
 		ldy  #>fmath_float1
 		jsr  MOVMF
@@ -617,53 +578,53 @@ func_ceil	.proc
 		jsr  FCOMP
 		cmp  #0
 		beq  +
-		lda  #<FL_FONE
-		ldy  #>FL_FONE
+		lda  #<FL_ONE_const
+		ldy  #>FL_ONE_const
 		jsr  FADD
 +		jmp  push_fac1_as_result
 		.pend

 func_any_f	.proc
 		inx
-		lda  c64.ESTACK_LO,x	; array size
-		sta  c64.SCRATCH_ZPB1
+		lda  P8ESTACK_LO,x	; array size
+		sta  P8ZP_SCRATCH_B1
 		asl  a
 		asl  a
 		clc
-		adc  c64.SCRATCH_ZPB1	; times 5 because of float
+		adc  P8ZP_SCRATCH_B1	; times 5 because of float
 		jmp  prog8_lib.func_any_b._entry
 		.pend

 func_all_f	.proc
 		inx
 		jsr  prog8_lib.peek_address
-		lda  c64.ESTACK_LO,x	; array size
-		sta  c64.SCRATCH_ZPB1
+		lda  P8ESTACK_LO,x	; array size
+		sta  P8ZP_SCRATCH_B1
 		asl  a
 		asl  a
 		clc
-		adc  c64.SCRATCH_ZPB1	; times 5 because of float
+		adc  P8ZP_SCRATCH_B1	; times 5 because of float
 		tay
 		dey
-		lda  (c64.SCRATCH_ZPWORD1),y
+-		lda  (P8ZP_SCRATCH_W1),y
 		clc
 		dey
-		adc  (c64.SCRATCH_ZPWORD1),y
+		adc  (P8ZP_SCRATCH_W1),y
 		dey
-		adc  (c64.SCRATCH_ZPWORD1),y
+		adc  (P8ZP_SCRATCH_W1),y
 		dey
-		adc  (c64.SCRATCH_ZPWORD1),y
+		adc  (P8ZP_SCRATCH_W1),y
 		dey
-		adc  (c64.SCRATCH_ZPWORD1),y
+		adc  (P8ZP_SCRATCH_W1),y
 		dey
 		cmp  #0
 		beq  +
-        cpy  #255
-        bne  -
+		cpy  #255
+        	bne  -
 		lda  #1
-		sta  c64.ESTACK_LO+1,x
+		sta  P8ESTACK_LO+1,x
 		rts
-+		sta  c64.ESTACK_LO+1,x
+		sta  P8ESTACK_LO+1,x
 		rts
 		.pend

@@ -674,26 +635,28 @@ func_max_f	.proc
 		ldy  #>_largest_neg_float
 _minmax_entry	jsr  MOVFM
 		jsr  prog8_lib.pop_array_and_lengthmin1Y
-		stx  c64.SCRATCH_ZPREGX
-		sty  c64.SCRATCH_ZPREG
-		lda  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
+		stx  floats_store_reg
+-		sty  P8ZP_SCRATCH_REG
+		lda  P8ZP_SCRATCH_W1
+		ldy  P8ZP_SCRATCH_W1+1
 		jsr  FCOMP
 _minmax_cmp	cmp  #255			; modified
 		bne  +
-		lda  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
+		lda  P8ZP_SCRATCH_W1
+		ldy  P8ZP_SCRATCH_W1+1
 		jsr  MOVFM
-+		lda  c64.SCRATCH_ZPWORD1
+		lda  P8ZP_SCRATCH_W1
 		clc
 		adc  #5
-		sta  c64.SCRATCH_ZPWORD1
+		sta  P8ZP_SCRATCH_W1
 		bcc  +
-		inc  c64.SCRATCH_ZPWORD1+1
-+		ldy  c64.SCRATCH_ZPREG
+		inc  P8ZP_SCRATCH_W1+1
+		ldy  P8ZP_SCRATCH_REG
 		dey
 		cpy  #255
 		bne  -
+		ldx  floats_store_reg
+		stx  P8ZP_SCRATCH_REG
 		jmp  push_fac1_as_result
 _largest_neg_float	.byte 255,255,255,255,255		; largest negative float -1.7014118345e+38
 		.pend
@@ -709,33 +672,91 @@ _largest_pos_float	.byte  255,127,255,255,255		; largest positive float
 		.pend

 func_sum_f	.proc
-		lda  #<FL_ZERO
-		ldy  #>FL_ZERO
+		lda  #<FL_ZERO_const
+		ldy  #>FL_ZERO_const
 		jsr  MOVFM
 		jsr  prog8_lib.pop_array_and_lengthmin1Y
-		stx  c64.SCRATCH_ZPREGX
-		sty  c64.SCRATCH_ZPREG
-		lda  c64.SCRATCH_ZPWORD1
-		ldy  c64.SCRATCH_ZPWORD1+1
+		stx  floats_store_reg
+-		sty  P8ZP_SCRATCH_REG
+		lda  P8ZP_SCRATCH_W1
+		ldy  P8ZP_SCRATCH_W1+1
 		jsr  FADD
-		ldy  c64.SCRATCH_ZPREG
+		ldy  P8ZP_SCRATCH_REG
 		dey
 		cpy  #255
 		beq  +
-		lda  c64.SCRATCH_ZPWORD1
+		lda  P8ZP_SCRATCH_W1
 		clc
 		adc  #5
-		sta  c64.SCRATCH_ZPWORD1
+		sta  P8ZP_SCRATCH_W1
 		bcc  -
-		inc  c64.SCRATCH_ZPWORD1+1
+		inc  P8ZP_SCRATCH_W1+1
 		bne  -
-+		jmp  push_fac1_as_result
+		ldx  floats_store_reg
+		stx  P8ZP_SCRATCH_REG
+		jmp  push_fac1_as_result
 		.pend

 sign_f		.proc
 		jsr  pop_float_fac1
 		jsr  SIGN
-		sta  c64.ESTACK_LO,x
+		sta  P8ESTACK_LO,x
 		dex
 		rts
 		.pend
+
+
+set_0_array_float	.proc
+		; -- set a float in an array to zero (index on stack, array in SCRATCH_ZPWORD1)
+		inx
+		lda  P8ESTACK_LO,x
+		asl  a
+		asl  a
+		clc
+		adc  P8ESTACK_LO,x
+		tay
+		lda  #0
+		sta  (P8ZP_SCRATCH_W1),y
+		iny
+		sta  (P8ZP_SCRATCH_W1),y
+		iny
+		sta  (P8ZP_SCRATCH_W1),y
+		iny
+		sta  (P8ZP_SCRATCH_W1),y
+		iny
+		sta  (P8ZP_SCRATCH_W1),y
+		rts
+		.pend
+
+
+set_array_float		.proc
+		; -- set a float in an array to a value (index on stack, float in SCRATCH_ZPWORD1, array in SCRATCH_ZPWORD2)
+		inx
+		lda  P8ESTACK_LO,x
+		asl  a
+		asl  a
+		clc
+		adc  P8ESTACK_LO,x
+		adc  P8ZP_SCRATCH_W2
+		ldy  P8ZP_SCRATCH_W2+1
+		bcc  +
+		iny
+		jmp  copy_float
+			; -- copies the 5 bytes of the mflt value pointed to by SCRATCH_ZPWORD1,
+			;    into the 5 bytes pointed to by A/Y.  Clobbers A,Y.
+		.pend
+
+
+swap_floats	.proc
+		; -- swap floats pointed to by SCRATCH_ZPWORD1, SCRATCH_ZPWORD2
+		ldy  #4
+-               lda  (P8ZP_SCRATCH_W1),y
+		pha
+		lda  (P8ZP_SCRATCH_W2),y
+		sta  (P8ZP_SCRATCH_W1),y
+		pla
+		sta  (P8ZP_SCRATCH_W2),y
+		dey
+		bpl  -
+		rts
+		.pend
@@ -4,14 +4,14 @@
 ;
 ; indent format: TABS, size=8

+%target c64
 %option enable_floats

-
-c64flt {
+floats {
 	; ---- this block contains C-64 floating point related functions ----

-		const  float  PI	= 3.141592653589793
-		const  float  TWOPI	= 6.283185307179586
+        const float  PI     = 3.141592653589793
+        const float  TWOPI  = 6.283185307179586


 ; ---- C64 basic and kernal ROM float constants and functions ----
@@ -34,13 +34,12 @@ c64flt {
 		&float  FL_PIHALF	= $e2e0  ; PI / 2
 		&float  FL_TWOPI	= $e2e5  ; 2 * PI
 		&float  FL_FR4		= $e2ea  ; .25
-		 float  FL_ZERO		= 0.0    ; oddly enough 0.0 isn't available in the kernel
+		; oddly enough, 0.0 isn't available in the kernel.


 ; note: fac1/2 might get clobbered even if not mentioned in the function's name.
 ; note: for subtraction and division, the left operand is in fac2, the right operand in fac1.

-; checked functions below:
 romsub $bba2 = MOVFM(uword mflpt @ AY) clobbers(A,Y)        ; load mflpt value from memory  in A/Y into fac1
 romsub $bba6 = FREADMEM() clobbers(A,Y)                     ; load mflpt value from memory  in $22/$23 into fac1
 romsub $ba8c = CONUPK(uword mflpt @ AY) clobbers(A,Y)       ; load mflpt value from memory  in A/Y into fac2
@@ -51,22 +50,22 @@ romsub $bc0f = MOVEF() clobbers(A,X)                        ; copy fac1 to fac2
 romsub $bbd4 = MOVMF(uword mflpt @ XY) clobbers(A,Y)        ; store fac1 to memory  X/Y as 5-byte mflpt

 ; fac1-> signed word in Y/A (might throw ILLEGAL QUANTITY)
-; (tip: use c64flt.FTOSWRDAY to get A/Y output; lo/hi switched to normal little endian order)
+; (tip: use floats.FTOSWRDAY to get A/Y output; lo/hi switched to normal little endian order)
 romsub $b1aa = FTOSWORDYA() clobbers(X) -> ubyte @ Y, ubyte @ A       ; note: calls AYINT.

 ; fac1 -> unsigned word in Y/A (might throw ILLEGAL QUANTITY) (result also in $14/15)
-; (tip: use c64flt.GETADRAY to get A/Y output; lo/hi switched to normal little endian order)
+; (tip: use floats.GETADRAY to get A/Y output; lo/hi switched to normal little endian order)
 romsub $b7f7 = GETADR() clobbers(X) -> ubyte @ Y, ubyte @ A

 romsub $bc9b = QINT() clobbers(A,X,Y)           ; fac1 -> 4-byte signed integer in 98-101 ($62-$65), with the MSB FIRST.
 romsub $b1bf = AYINT() clobbers(A,X,Y)          ; fac1-> signed word in 100-101 ($64-$65) MSB FIRST. (might throw ILLEGAL QUANTITY)

 ; GIVAYF: signed word in Y/A (note different lsb/msb order) -> float in fac1
-; (tip: use c64flt.GIVAYFAY to use A/Y input; lo/hi switched to normal order)
-; there is also c64flt.GIVUAYFAY - unsigned word in A/Y (lo/hi) to fac1
-; there is also c64flt.FREADS32  that reads from 98-101 ($62-$65) MSB FIRST
-; there is also c64flt.FREADUS32  that reads from 98-101 ($62-$65) MSB FIRST
-; there is also c64flt.FREADS24AXY  that reads signed int24 into fac1 from A/X/Y (lo/mid/hi bytes)
+; (tip: use floats.GIVAYFAY to use A/Y input; lo/hi switched to normal order)
+; there is also floats.GIVUAYFAY - unsigned word in A/Y (lo/hi) to fac1
+; there is also floats.FREADS32  that reads from 98-101 ($62-$65) MSB FIRST
+; there is also floats.FREADUS32  that reads from 98-101 ($62-$65) MSB FIRST
+; there is also floats.FREADS24AXY  that reads signed int24 into fac1 from A/X/Y (lo/mid/hi bytes)
 romsub $b391 = GIVAYF(ubyte lo @ Y, ubyte hi @ A) clobbers(A,X,Y)

 romsub $b3a2 = FREADUY(ubyte value @ Y) clobbers(A,X,Y)     ; 8 bit unsigned Y -> float in fac1
@@ -90,6 +89,7 @@ romsub $bb12 = FDIVT() clobbers(A,X,Y)                      ; fac1 = fac2/fac1
 romsub $bb0f = FDIV(uword mflpt @ AY) clobbers(A,X,Y)       ; fac1 = mflpt in A/Y / fac1  (remainder in fac2)
 romsub $bf7b = FPWRT() clobbers(A,X,Y)                      ; fac1 = fac2 ** fac1
 romsub $bf78 = FPWR(uword mflpt @ AY) clobbers(A,X,Y)       ; fac1 = fac2 ** mflpt from A/Y
+romsub $bd7e = FINLOG(byte value @A) clobbers (A, X, Y)     ; fac1 += signed byte in A

 romsub $aed4 = NOTOP() clobbers(A,X,Y)                      ; fac1 = NOT(fac1)
 romsub $bccc = INT() clobbers(A,X,Y)                        ; INT() truncates, use FADDH first to round instead of trunc
@@ -162,9 +162,9 @@ asmsub  GIVUAYFAY  (uword value @ AY) clobbers(A,X,Y)  {
 asmsub  GIVAYFAY  (uword value @ AY) clobbers(A,X,Y)  {
 	; ---- signed 16 bit word in A/Y (lo/hi) to float in fac1
 	%asm {{
-		sta  c64.SCRATCH_ZPREG
+		sta  P8ZP_SCRATCH_REG
 		tya
-		ldy  c64.SCRATCH_ZPREG
+		ldy  P8ZP_SCRATCH_REG
 		jmp  GIVAYF		; this uses the inverse order, Y/A
 	}}
 }
@@ -173,9 +173,9 @@ asmsub  FTOSWRDAY  () clobbers(X) -> uword @ AY  {
 	; ---- fac1 to signed word in A/Y
 	%asm {{
 		jsr  FTOSWORDYA	; note the inverse Y/A order
-		sta  c64.SCRATCH_ZPREG
+		sta  P8ZP_SCRATCH_REG
 		tya
-		ldy  c64.SCRATCH_ZPREG
+		ldy  P8ZP_SCRATCH_REG
 		rts
 	}}
 }
@@ -184,41 +184,34 @@ asmsub  GETADRAY  () clobbers(X) -> uword @ AY  {
 	; ---- fac1 to unsigned word in A/Y
 	%asm {{
 		jsr  GETADR		; this uses the inverse order, Y/A
-		sta  c64.SCRATCH_ZPB1
+		sta  P8ZP_SCRATCH_B1
 		tya
-		ldy  c64.SCRATCH_ZPB1
+		ldy  P8ZP_SCRATCH_B1
 		rts
 	}}
 }

 sub  print_f  (float value) {
-	; ---- prints the floating point value (without a newline) using basic rom routines.
+	; ---- prints the floating point value (without a newline).
 	%asm {{
-		stx  c64.SCRATCH_ZPREGX
+		stx  floats_store_reg
 		lda  #<value
 		ldy  #>value
 		jsr  MOVFM		; load float into fac1
 		jsr  FOUT		; fac1 to string in A/Y
-		jsr  c64.STROUT			; print string in A/Y
-		ldx  c64.SCRATCH_ZPREGX
-		rts
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		ldy  #0
+-		lda  (P8ZP_SCRATCH_W1),y
+		beq  +
+		jsr  c64.CHROUT
+		iny
+		bne  -
+		ldx  floats_store_reg
+		rts
 	}}
 }

-sub  print_fln  (float value) {
-	; ---- prints the floating point value (with a newline at the end) using basic rom routines
-	%asm {{
-		stx  c64.SCRATCH_ZPREGX
-		lda  #<print_fln_value
-		ldy  #>print_fln_value
-		jsr  MOVFM		; load float into fac1
-		jsr  FPRINTLN		; print fac1 with newline
-		ldx  c64.SCRATCH_ZPREGX
-		rts
-	}}
+%asminclude "library:c64/floats.asm", ""

 }
-
-%asminclude "library:c64floats.asm", ""
-
-}  ; ------ end of block c64flt
@@ -0,0 +1,244 @@
+%target c64
+%import textio
+
+; bitmap pixel graphics module for the C64
+; only black/white monchrome 320x200 for now
+; assumes bitmap screen memory is $2000-$3fff
+
+graphics {
+    const uword BITMAP_ADDRESS = $2000
+    const uword WIDTH = 320
+    const ubyte HEIGHT = 200
+
+    sub enable_bitmap_mode() {
+        ; enable bitmap screen, erase it and set colors to black/white.
+        c64.SCROLY |= %00100000
+        c64.VMCSB = (c64.VMCSB & %11110000) | %00001000   ; $2000-$3fff
+        clear_screen(1, 0)
+    }
+
+    sub clear_screen(ubyte pixelcolor, ubyte bgcolor) {
+        memset(BITMAP_ADDRESS, 320*200/8, 0)
+        txt.fill_screen(pixelcolor << 4 | bgcolor, 0)
+    }
+
+    sub line(uword @zp x1, ubyte @zp y1, uword @zp x2, ubyte @zp y2) {
+        ; Bresenham algorithm.
+        ; This code special cases various quadrant loops to allow simple ++ and -- operations.
+        ; TODO rewrite this in optimized assembly
+        if y1>y2 {
+            ; make sure dy is always positive to avoid 8 instead of just 4 special cases
+            swap(x1, x2)
+            swap(y1, y2)
+        }
+        word @zp d = 0
+        ubyte positive_ix = true
+        word @zp dx = x2 - x1 as word
+        word @zp dy = y2 as word - y1 as word
+        if dx < 0 {
+            dx = -dx
+            positive_ix = false
+        }
+        dx *= 2
+        dy *= 2
+        internal_plotx = x1
+
+        if dx >= dy {
+            if positive_ix {
+                repeat {
+                    internal_plot(y1)
+                    if internal_plotx==x2
+                        return
+                    internal_plotx++
+                    d += dy
+                    if d > dx {
+                        y1++
+                        d -= dx
+                    }
+                }
+            } else {
+                repeat {
+                    internal_plot(y1)
+                    if internal_plotx==x2
+                        return
+                    internal_plotx--
+                    d += dy
+                    if d > dx {
+                        y1++
+                        d -= dx
+                    }
+                }
+            }
+        }
+        else {
+            if positive_ix {
+                repeat {
+                    internal_plot(y1)
+                    if y1 == y2
+                        return
+                    y1++
+                    d += dx
+                    if d > dy {
+                        internal_plotx++
+                        d -= dy
+                    }
+                }
+            } else {
+                repeat {
+                    internal_plot(y1)
+                    if y1 == y2
+                        return
+                    y1++
+                    d += dx
+                    if d > dy {
+                        internal_plotx--
+                        d -= dy
+                    }
+                }
+            }
+        }
+    }
+
+    sub circle(uword xcenter, ubyte ycenter, ubyte radius) {
+        ; Midpoint algorithm
+        ubyte @zp ploty
+        ubyte @zp xx = radius
+        ubyte @zp yy = 0
+        byte @zp decisionOver2 = 1-xx as byte
+
+        while xx>=yy {
+            internal_plotx = xcenter + xx
+            ploty = ycenter + yy
+            internal_plot(ploty)
+            internal_plotx = xcenter - xx
+            internal_plot(ploty)
+            internal_plotx = xcenter + xx
+            ploty = ycenter - yy
+            internal_plot(ploty)
+            internal_plotx = xcenter - xx
+            internal_plot(ploty)
+            internal_plotx = xcenter + yy
+            ploty = ycenter + xx
+            internal_plot(ploty)
+            internal_plotx = xcenter - yy
+            internal_plot(ploty)
+            internal_plotx = xcenter + yy
+            ploty = ycenter - xx
+            internal_plot(ploty)
+            internal_plotx = xcenter - yy
+            internal_plot(ploty)
+            yy++
+            if decisionOver2<=0
+                decisionOver2 += 2*yy+1
+            else {
+                xx--
+                decisionOver2 += 2*(yy-xx)+1
+            }
+        }
+    }
+
+    sub disc(uword xcenter, ubyte ycenter, ubyte radius) {
+        ; Midpoint algorithm, filled
+        ubyte xx = radius
+        ubyte yy = 0
+        byte decisionOver2 = 1-xx as byte
+
+        while xx>=yy {
+            ubyte ycenter_plus_yy = ycenter + yy
+            ubyte ycenter_min_yy = ycenter - yy
+            ubyte ycenter_plus_xx = ycenter + xx
+            ubyte ycenter_min_xx = ycenter - xx
+
+            for internal_plotx in xcenter to xcenter+xx {
+                internal_plot(ycenter_plus_yy)
+                internal_plot(ycenter_min_yy)
+            }
+            for internal_plotx in xcenter-xx to xcenter-1 {
+                internal_plot(ycenter_plus_yy)
+                internal_plot(ycenter_min_yy)
+            }
+            for internal_plotx in xcenter to xcenter+yy {
+                internal_plot(ycenter_plus_xx)
+                internal_plot(ycenter_min_xx)
+            }
+            for internal_plotx in xcenter-yy to xcenter {
+                internal_plot(ycenter_plus_xx)
+                internal_plot(ycenter_min_xx)
+            }
+            yy++
+            if decisionOver2<=0
+                decisionOver2 += 2*yy+1
+            else {
+                xx--
+                decisionOver2 += 2*(yy-xx)+1
+            }
+        }
+    }
+
+
+; here is the non-asm code for the plot routine below:
+;    sub plot_nonasm(uword px, ubyte py) {
+;        ubyte[] ormask = [128, 64, 32, 16, 8, 4, 2, 1]
+;        uword addr = BITMAP_ADDRESS + 320*(py>>3) + (py & 7) + (px & %0000000111111000)
+;        @(addr) |= ormask[lsb(px) & 7]
+;    }
+
+    asmsub  plot(uword plotx @XY, ubyte ploty @A) clobbers (A, X, Y) {
+        %asm {{
+            stx  internal_plotx
+            sty  internal_plotx+1
+            jmp  internal_plot
+        }}
+    }
+
+    ; for efficiency of internal algorithms here is the internal plot routine
+    ; that takes the plotx coordinate in a separate variable instead of the XY register pair:
+
+    uword internal_plotx     ; 0..319        ; separate 'parameter' for internal_plot()
+
+    asmsub  internal_plot(ubyte ploty @A) clobbers (A, X, Y) {      ; internal_plotx is 16 bits 0 to 319... doesn't fit in a register
+        %asm {{
+        tay
+        lda  internal_plotx+1
+        sta  P8ZP_SCRATCH_W2+1
+        lsr  a            ; 0
+        sta  P8ZP_SCRATCH_W2
+        lda  internal_plotx
+        pha
+        and  #7
+        tax
+
+        lda  _y_lookup_lo,y
+        clc
+        adc  P8ZP_SCRATCH_W2
+        sta  P8ZP_SCRATCH_W2
+        lda  _y_lookup_hi,y
+        adc  P8ZP_SCRATCH_W2+1
+        sta  P8ZP_SCRATCH_W2+1
+
+        pla     ; internal_plotx
+        and  #%11111000
+        tay
+        lda  (P8ZP_SCRATCH_W2),y
+        ora  _ormask,x
+        sta  (P8ZP_SCRATCH_W2),y
+        rts
+
+_ormask     .byte 128, 64, 32, 16, 8, 4, 2, 1
+
+; note: this can be even faster if we also have a 256 byte x-lookup table, but hey.
+; see http://codebase64.org/doku.php?id=base:various_techniques_to_calculate_adresses_fast_common_screen_formats_for_pixel_graphics
+; the y lookup tables encodes this formula:  BITMAP_ADDRESS + 320*(py>>3) + (py & 7)    (y from 0..199)
+; We use the 64tass syntax for range expressions to calculate this table on assembly time.
+
+_plot_y_values := $2000 + 320*(range(200)>>3) + (range(200) & 7)
+
+_y_lookup_lo    .byte  <_plot_y_values
+_y_lookup_hi    .byte  >_plot_y_values
+
+        }}
+    }
+
+}
+
+
@@ -5,20 +5,13 @@
 ;
 ; indent format: TABS, size=8

+%target c64

 c64 {
-        const  uword  ESTACK_LO = $ce00     ; evaluation stack (lsb)
-        const  uword  ESTACK_HI = $cf00     ; evaluation stack (msb)
-        &ubyte  SCRATCH_ZPB1    = $02       ; scratch byte 1 in ZP
-        &ubyte  SCRATCH_ZPREG   = $03       ; scratch register in ZP
-        &ubyte  SCRATCH_ZPREGX  = $fa       ; temp storage for X register (stack pointer)
-        &uword  SCRATCH_ZPWORD1 = $fb       ; scratch word in ZP ($fb/$fc)
-        &uword  SCRATCH_ZPWORD2 = $fd       ; scratch word in ZP ($fd/$fe)
-
-
        &ubyte  TIME_HI         = $a0       ; software jiffy clock, hi byte
        &ubyte  TIME_MID        = $a1       ;  .. mid byte
        &ubyte  TIME_LO         = $a2       ;    .. lo byte. Updated by IRQ every 1/60 sec
+        &ubyte  STATUS          = $90       ; kernel status variable for I/O
        &ubyte  STKEY           = $91       ; various keyboard statuses (updated by IRQ)
        &ubyte  SFDX            = $cb       ; current key pressed (matrix value) (updated by IRQ)

@@ -183,19 +176,11 @@ c64 {
 ; ---- end of SID registers ----


-
-; ---- C64 basic routines ----
-
-romsub $E544 = CLEARSCR() clobbers(A,X,Y)       ; clear the screen
-romsub $E566 = HOMECRSR() clobbers(A,X,Y)       ; cursor to top left of screen
-
-
-; ---- end of C64 basic routines ----
-
-
-; ---- C64 kernal routines ----
+; ---- C64 ROM kernal routines ----

 romsub $AB1E = STROUT(uword strptr @ AY) clobbers(A, X, Y)      ; print null-terminated string (use c64scr.print instead)
+romsub $E544 = CLEARSCR() clobbers(A,X,Y)                       ; clear the screen
+romsub $E566 = HOMECRSR() clobbers(A,X,Y)                       ; cursor to top left of screen
 romsub $EA31 = IRQDFRT() clobbers(A,X,Y)                        ; default IRQ routine
 romsub $EA81 = IRQDFEND() clobbers(A,X,Y)                       ; default IRQ end/cleanup
 romsub $FF81 = CINT() clobbers(A,X,Y)                           ; (alias: SCINIT) initialize screen editor and video chip
@@ -238,6 +223,217 @@ romsub $FFED = SCREEN() -> ubyte @ X, ubyte @ Y                 ; read number of
 romsub $FFF0 = PLOT(ubyte col @ Y, ubyte row @ X, ubyte dir @ Pc) -> ubyte @ X, ubyte @ Y       ; read/set position of cursor on screen.  Use c64scr.plot for a 'safe' wrapper that preserves X.
 romsub $FFF3 = IOBASE() -> uword @ XY                           ; read base address of I/O devices

-; ---- end of C64 kernal routines ----
+; ---- end of C64 ROM kernal routines ----
+
+
+; ---- C64 specific system utility routines: ----
+
+asmsub  init_system()  {
+    ; Initializes the machine to a sane starting state.
+    ; Called automatically by the loader program logic.
+    ; This means that the BASIC, KERNAL and CHARGEN ROMs are banked in,
+    ; the VIC, SID and CIA chips are reset, screen is cleared, and the default IRQ is set.
+    ; Also a different color scheme is chosen to identify ourselves a little.
+    ; Uppercase charset is activated, and all three registers set to 0, status flags cleared.
+    %asm {{
+        sei
+        cld
+        lda  #%00101111
+        sta  $00
+        lda  #%00100111
+        sta  $01
+        jsr  c64.IOINIT
+        jsr  c64.RESTOR
+        jsr  c64.CINT
+        lda  #6
+        sta  c64.EXTCOL
+        lda  #7
+        sta  c64.COLOR
+        lda  #0
+        sta  c64.BGCOL0
+        tax
+        tay
+        clc
+        clv
+        cli
+        rts
+    }}
+}
+
+asmsub  reset_system()  {
+    ; Soft-reset the system back to Basic prompt.
+    %asm {{
+        sei
+        lda  #14
+        sta  $01        ; bank the kernal in
+        jmp  (c64.RESET_VEC)
+    }}
+}
+
+asmsub  set_irqvec_excl() clobbers(A)  {
+	%asm {{
+		sei
+		lda  #<_irq_handler
+		sta  c64.CINV
+		lda  #>_irq_handler
+		sta  c64.CINV+1
+		cli
+		rts
+_irq_handler	jsr  set_irqvec._irq_handler_init
+		jsr  irq.irq
+		jsr  set_irqvec._irq_handler_end
+		lda  #$ff
+		sta  c64.VICIRQ			; acknowledge raster irq
+		lda  c64.CIA1ICR		; acknowledge CIA1 interrupt
+		jmp  c64.IRQDFEND		; end irq processing - don't call kernel
+	}}
+}
+
+asmsub  set_irqvec() clobbers(A)  {
+	%asm {{
+		sei
+		lda  #<_irq_handler
+		sta  c64.CINV
+		lda  #>_irq_handler
+		sta  c64.CINV+1
+		cli
+		rts
+_irq_handler    jsr  _irq_handler_init
+		jsr  irq.irq
+		jsr  _irq_handler_end
+		jmp  c64.IRQDFRT		; continue with normal kernel irq routine
+
+_irq_handler_init
+		; save all zp scratch registers and the X register as these might be clobbered by the irq routine
+		stx  IRQ_X_REG
+		lda  P8ZP_SCRATCH_B1
+		sta  IRQ_SCRATCH_ZPB1
+		lda  P8ZP_SCRATCH_REG
+		sta  IRQ_SCRATCH_ZPREG
+		lda  P8ZP_SCRATCH_W1
+		sta  IRQ_SCRATCH_ZPWORD1
+		lda  P8ZP_SCRATCH_W1+1
+		sta  IRQ_SCRATCH_ZPWORD1+1
+		lda  P8ZP_SCRATCH_W2
+		sta  IRQ_SCRATCH_ZPWORD2
+		lda  P8ZP_SCRATCH_W2+1
+		sta  IRQ_SCRATCH_ZPWORD2+1
+		; stack protector; make sure we don't clobber the top of the evaluation stack
+		dex
+		dex
+		dex
+		dex
+		dex
+		dex
+		cld
+		rts
+
+_irq_handler_end
+		; restore all zp scratch registers and the X register
+		lda  IRQ_SCRATCH_ZPB1
+		sta  P8ZP_SCRATCH_B1
+		lda  IRQ_SCRATCH_ZPREG
+		sta  P8ZP_SCRATCH_REG
+		lda  IRQ_SCRATCH_ZPWORD1
+		sta  P8ZP_SCRATCH_W1
+		lda  IRQ_SCRATCH_ZPWORD1+1
+		sta  P8ZP_SCRATCH_W1+1
+		lda  IRQ_SCRATCH_ZPWORD2
+		sta  P8ZP_SCRATCH_W2
+		lda  IRQ_SCRATCH_ZPWORD2+1
+		sta  P8ZP_SCRATCH_W2+1
+		ldx  IRQ_X_REG
+		rts
+
+IRQ_X_REG		.byte  0
+IRQ_SCRATCH_ZPB1	.byte  0
+IRQ_SCRATCH_ZPREG	.byte  0
+IRQ_SCRATCH_ZPWORD1	.word  0
+IRQ_SCRATCH_ZPWORD2	.word  0
+
+		}}
+}
+
+asmsub  restore_irqvec() {
+	%asm {{
+		sei
+		lda  #<c64.IRQDFRT
+		sta  c64.CINV
+		lda  #>c64.IRQDFRT
+		sta  c64.CINV+1
+		lda  #0
+		sta  c64.IREQMASK	; disable raster irq
+		lda  #%10000001
+		sta  c64.CIA1ICR	; restore CIA1 irq
+		cli
+		rts
+	}}
+}
+
+asmsub  set_rasterirq(uword rasterpos @ AY) clobbers(A) {
+	%asm {{
+		sei
+		jsr  _setup_raster_irq
+		lda  #<_raster_irq_handler
+		sta  c64.CINV
+		lda  #>_raster_irq_handler
+		sta  c64.CINV+1
+		cli
+		rts
+
+_raster_irq_handler
+		jsr  set_irqvec._irq_handler_init
+		jsr  irq.irq
+		jsr  set_irqvec._irq_handler_end
+		lda  #$ff
+		sta  c64.VICIRQ			; acknowledge raster irq
+		jmp  c64.IRQDFRT
+
+_setup_raster_irq
+		pha
+		lda  #%01111111
+		sta  c64.CIA1ICR    ; "switch off" interrupts signals from cia-1
+		sta  c64.CIA2ICR    ; "switch off" interrupts signals from cia-2
+		and  c64.SCROLY
+		sta  c64.SCROLY     ; clear most significant bit of raster position
+		lda  c64.CIA1ICR    ; ack previous irq
+		lda  c64.CIA2ICR    ; ack previous irq
+		pla
+		sta  c64.RASTER     ; set the raster line number where interrupt should occur
+		cpy  #0
+		beq  +
+		lda  c64.SCROLY
+		ora  #%10000000
+		sta  c64.SCROLY     ; set most significant bit of raster position
+		lda  #%00000001
+		sta  c64.IREQMASK   ;enable raster interrupt signals from vic
+		rts
+	}}
+}
+
+asmsub  set_rasterirq_excl(uword rasterpos @ AY) clobbers(A) {
+	%asm {{
+		sei
+		jsr  set_rasterirq._setup_raster_irq
+		lda  #<_raster_irq_handler
+		sta  c64.CINV
+		lda  #>_raster_irq_handler
+		sta  c64.CINV+1
+		cli
+		rts
+
+_raster_irq_handler
+		jsr  set_irqvec._irq_handler_init
+		jsr  irq.irq
+		jsr  set_irqvec._irq_handler_end
+		lda  #$ff
+		sta  c64.VICIRQ			; acknowledge raster irq
+		jmp  c64.IRQDFEND		; end irq processing - don't call kernel
+
+	}}
+}
+
+; ---- end of C64 specific system utility routines ----
+

 }
@@ -0,0 +1,587 @@
+; Prog8 definitions for the Text I/O and Screen routines for the Commodore-64
+;
+; Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+;
+; indent format: TABS, size=8
+
+%target c64
+%import syslib
+%import conv
+
+
+txt {
+
+const ubyte DEFAULT_WIDTH = 40
+const ubyte DEFAULT_HEIGHT = 25
+
+
+sub  clear_screen() {
+    clear_screenchars(' ')
+}
+
+asmsub  fill_screen (ubyte char @ A, ubyte color @ Y) clobbers(A)  {
+	; ---- fill the character screen with the given fill character and character color.
+	;      (assumes screen and color matrix are at their default addresses)
+
+	%asm {{
+		pha
+		tya
+		jsr  clear_screencolors
+		pla
+		jsr  clear_screenchars
+		rts
+        }}
+
+}
+
+asmsub  clear_screenchars (ubyte char @ A) clobbers(Y)  {
+	; ---- clear the character screen with the given fill character (leaves colors)
+	;      (assumes screen matrix is at the default address)
+	%asm {{
+		ldy  #0
+_loop		sta  c64.Screen,y
+		sta  c64.Screen+$0100,y
+		sta  c64.Screen+$0200,y
+		sta  c64.Screen+$02e8,y
+		iny
+		bne  _loop
+		rts
+        }}
+}
+
+asmsub  clear_screencolors (ubyte color @ A) clobbers(Y)  {
+	; ---- clear the character screen colors with the given color (leaves characters).
+	;      (assumes color matrix is at the default address)
+	%asm {{
+		ldy  #0
+_loop		sta  c64.Colors,y
+		sta  c64.Colors+$0100,y
+		sta  c64.Colors+$0200,y
+		sta  c64.Colors+$02e8,y
+		iny
+		bne  _loop
+		rts
+        }}
+}
+
+sub color (ubyte txtcol) {
+    c64.COLOR = txtcol
+}
+
+sub lowercase() {
+    c64.VMCSB |= 2
+}
+
+sub uppercase() {
+    c64.VMCSB &= ~2
+}
+
+asmsub  scroll_left  (ubyte alsocolors @ Pc) clobbers(A, Y)  {
+	; ---- scroll the whole screen 1 character to the left
+	;      contents of the rightmost column are unchanged, you should clear/refill this yourself
+	;      Carry flag determines if screen color data must be scrolled too
+
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		bcs  +
+		jmp  _scroll_screen
+
+               ; scroll the color memory
+		ldx  #0
+		ldy  #38
+-
+	.for row=0, row<=24, row+=1
+		lda  c64.Colors + 40*row + 1,x
+		sta  c64.Colors + 40*row,x
+	.next
+		inx
+		dey
+		bpl  -
+
+_scroll_screen  ; scroll the screen memory
+		ldx  #0
+		ldy  #38
+-
+	.for row=0, row<=24, row+=1
+		lda  c64.Screen + 40*row + 1,x
+		sta  c64.Screen + 40*row,x
+	.next
+		inx
+		dey
+		bpl  -
+
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  scroll_right  (ubyte alsocolors @ Pc) clobbers(A)  {
+	; ---- scroll the whole screen 1 character to the right
+	;      contents of the leftmost column are unchanged, you should clear/refill this yourself
+	;      Carry flag determines if screen color data must be scrolled too
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		bcs  +
+		jmp  _scroll_screen
+
+               ; scroll the color memory
+		ldx  #38
+-
+	.for row=0, row<=24, row+=1
+		lda  c64.Colors + 40*row + 0,x
+		sta  c64.Colors + 40*row + 1,x
+	.next
+		dex
+		bpl  -
+
+_scroll_screen  ; scroll the screen memory
+		ldx  #38
+-
+	.for row=0, row<=24, row+=1
+		lda  c64.Screen + 40*row + 0,x
+		sta  c64.Screen + 40*row + 1,x
+	.next
+		dex
+		bpl  -
+
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  scroll_up  (ubyte alsocolors @ Pc) clobbers(A)  {
+	; ---- scroll the whole screen 1 character up
+	;      contents of the bottom row are unchanged, you should refill/clear this yourself
+	;      Carry flag determines if screen color data must be scrolled too
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		bcs  +
+		jmp  _scroll_screen
+
+               ; scroll the color memory
+		ldx #39
+-
+	.for row=1, row<=24, row+=1
+		lda  c64.Colors + 40*row,x
+		sta  c64.Colors + 40*(row-1),x
+	.next
+		dex
+		bpl  -
+
+_scroll_screen  ; scroll the screen memory
+		ldx #39
+-
+	.for row=1, row<=24, row+=1
+		lda  c64.Screen + 40*row,x
+		sta  c64.Screen + 40*(row-1),x
+	.next
+		dex
+		bpl  -
+
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  scroll_down  (ubyte alsocolors @ Pc) clobbers(A)  {
+	; ---- scroll the whole screen 1 character down
+	;      contents of the top row are unchanged, you should refill/clear this yourself
+	;      Carry flag determines if screen color data must be scrolled too
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		bcs  +
+		jmp  _scroll_screen
+
+               ; scroll the color memory
+		ldx #39
+-
+	.for row=23, row>=0, row-=1
+		lda  c64.Colors + 40*row,x
+		sta  c64.Colors + 40*(row+1),x
+	.next
+		dex
+		bpl  -
+
+_scroll_screen  ; scroll the screen memory
+		ldx #39
+-
+	.for row=23, row>=0, row-=1
+		lda  c64.Screen + 40*row,x
+		sta  c64.Screen + 40*(row+1),x
+	.next
+		dex
+		bpl  -
+
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+romsub $FFD2 = chrout(ubyte char @ A)    ; for consistency. You can also use c64.CHROUT directly ofcourse.
+
+asmsub  print (str text @ AY) clobbers(A,Y)  {
+	; ---- print null terminated string from A/Y
+	; note: the compiler contains an optimization that will replace
+	;       a call to this subroutine with a string argument of just one char,
+	;       by just one call to c64.CHROUT of that single char.
+	%asm {{
+		sta  P8ZP_SCRATCH_B1
+		sty  P8ZP_SCRATCH_REG
+		ldy  #0
+-		lda  (P8ZP_SCRATCH_B1),y
+		beq  +
+		jsr  c64.CHROUT
+		iny
+		bne  -
+		rts
+	}}
+}
+
+asmsub  print_ub0  (ubyte value @ A) clobbers(A,Y)  {
+	; ---- print the ubyte in A in decimal form, with left padding 0s (3 positions total)
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		jsr  conv.ubyte2decimal
+		pha
+		tya
+		jsr  c64.CHROUT
+		pla
+		jsr  c64.CHROUT
+		txa
+		jsr  c64.CHROUT
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  print_ub  (ubyte value @ A) clobbers(A,Y)  {
+	; ---- print the ubyte in A in decimal form, without left padding 0s
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		jsr  conv.ubyte2decimal
+_print_byte_digits
+		pha
+		cpy  #'0'
+		beq  +
+		tya
+		jsr  c64.CHROUT
+		pla
+		jsr  c64.CHROUT
+		jmp  _ones
+       pla
+        cmp  #'0'
+        beq  _ones
+        jsr  c64.CHROUT
+_ones   txa
+		jsr  c64.CHROUT
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  print_b  (byte value @ A) clobbers(A,Y)  {
+	; ---- print the byte in A in decimal form, without left padding 0s
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		pha
+		cmp  #0
+		bpl  +
+		lda  #'-'
+		jsr  c64.CHROUT
+		pla
+		jsr  conv.byte2decimal
+		jmp  print_ub._print_byte_digits
+	}}
+}
+
+asmsub  print_ubhex  (ubyte value @ A, ubyte prefix @ Pc) clobbers(A,Y)  {
+	; ---- print the ubyte in A in hex form (if Carry is set, a radix prefix '$' is printed as well)
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		bcc  +
+		pha
+		lda  #'$'
+		jsr  c64.CHROUT
+		pla
+		jsr  conv.ubyte2hex
+		jsr  c64.CHROUT
+		tya
+		jsr  c64.CHROUT
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  print_ubbin  (ubyte value @ A, ubyte prefix @ Pc) clobbers(A,Y)  {
+	; ---- print the ubyte in A in binary form (if Carry is set, a radix prefix '%' is printed as well)
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		sta  P8ZP_SCRATCH_B1
+		bcc  +
+		lda  #'%'
+		jsr  c64.CHROUT
+		ldy  #8
+-		lda  #'0'
+		asl  P8ZP_SCRATCH_B1
+		bcc  +
+		lda  #'1'
+		jsr  c64.CHROUT
+		dey
+		bne  -
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  print_uwbin  (uword value @ AY, ubyte prefix @ Pc) clobbers(A,Y)  {
+	; ---- print the uword in A/Y in binary form (if Carry is set, a radix prefix '%' is printed as well)
+	%asm {{
+		pha
+		tya
+		jsr  print_ubbin
+		pla
+		clc
+		jmp  print_ubbin
+	}}
+}
+
+asmsub  print_uwhex  (uword value @ AY, ubyte prefix @ Pc) clobbers(A,Y)  {
+	; ---- print the uword in A/Y in hexadecimal form (4 digits)
+	;      (if Carry is set, a radix prefix '$' is printed as well)
+	%asm {{
+		pha
+		tya
+		jsr  print_ubhex
+		pla
+		clc
+		jmp  print_ubhex
+	}}
+}
+
+asmsub  print_uw0  (uword value @ AY) clobbers(A,Y)  {
+	; ---- print the uword in A/Y in decimal form, with left padding 0s (5 positions total)
+	%asm {{
+	    stx  P8ZP_SCRATCH_REG
+		jsr  conv.uword2decimal
+		ldy  #0
+-		lda  conv.uword2decimal.decTenThousands,y
+        beq  +
+		jsr  c64.CHROUT
+		iny
+		bne  -
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  print_uw  (uword value @ AY) clobbers(A,Y)  {
+	; ---- print the uword in A/Y in decimal form, without left padding 0s
+	%asm {{
+	    stx  P8ZP_SCRATCH_REG
+		jsr  conv.uword2decimal
+		ldx  P8ZP_SCRATCH_REG
+		ldy  #0
+-		lda  conv.uword2decimal.decTenThousands,y
+		beq  _allzero
+		cmp  #'0'
+		bne  _gotdigit
+		iny
+		bne  -
+
+_gotdigit
+		jsr  c64.CHROUT
+		iny
+		lda  conv.uword2decimal.decTenThousands,y
+		bne  _gotdigit
+		rts
+_allzero
+        lda  #'0'
+        jmp  c64.CHROUT
+	}}
+}
+
+asmsub  print_w  (word value @ AY) clobbers(A,Y)  {
+	; ---- print the (signed) word in A/Y in decimal form, without left padding 0's
+	%asm {{
+		cpy  #0
+		bpl  +
+		pha
+		lda  #'-'
+		jsr  c64.CHROUT
+		tya
+		eor  #255
+		tay
+		pla
+		eor  #255
+		clc
+		adc  #1
+		bcc  +
+		iny
+		jmp  print_uw
+	}}
+}
+
+asmsub  input_chars  (uword buffer @ AY) clobbers(A) -> ubyte @ Y  {
+	; ---- Input a string (max. 80 chars) from the keyboard. Returns length in Y. (string is terminated with a 0 byte as well)
+	;      It assumes the keyboard is selected as I/O channel!
+
+	%asm {{
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		ldy  #0				; char counter = 0
+-		jsr  c64.CHRIN
+		cmp  #$0d			; return (ascii 13) pressed?
+		beq  +				; yes, end.
+		sta  (P8ZP_SCRATCH_W1),y	; else store char in buffer
+		iny
+		bne  -
+		lda  #0
+		sta  (P8ZP_SCRATCH_W1),y	; finish string with 0 byte
+		rts
+
+	}}
+}
+
+asmsub  setchr  (ubyte col @X, ubyte row @Y, ubyte character @A) clobbers(A, Y)  {
+	; ---- sets the character in the screen matrix at the given position
+	%asm {{
+		pha
+		tya
+		asl  a
+		tay
+		lda  _screenrows+1,y
+		sta  _mod+2
+		txa
+		clc
+		adc  _screenrows,y
+		sta  _mod+1
+		bcc  +
+		inc  _mod+2
+		pla
+_mod		sta  $ffff		; modified
+		rts
+
+_screenrows	.word  $0400 + range(0, 1000, 40)
+	}}
+}
+
+asmsub  getchr  (ubyte col @A, ubyte row @Y) clobbers(Y) -> ubyte @ A {
+	; ---- get the character in the screen matrix at the given location
+	%asm  {{
+		pha
+		tya
+		asl  a
+		tay
+		lda  setchr._screenrows+1,y
+		sta  _mod+2
+		pla
+		clc
+		adc  setchr._screenrows,y
+		sta  _mod+1
+		bcc  _mod
+		inc  _mod+2
+_mod		lda  $ffff		; modified
+		rts
+	}}
+}
+
+asmsub  setclr  (ubyte col @X, ubyte row @Y, ubyte color @A) clobbers(A, Y)  {
+	; ---- set the color in A on the screen matrix at the given position
+	%asm {{
+		pha
+		tya
+		asl  a
+		tay
+		lda  _colorrows+1,y
+		sta  _mod+2
+		txa
+		clc
+		adc  _colorrows,y
+		sta  _mod+1
+		bcc  +
+		inc  _mod+2
+		pla
+_mod		sta  $ffff		; modified
+		rts
+
+_colorrows	.word  $d800 + range(0, 1000, 40)
+	}}
+}
+
+asmsub  getclr  (ubyte col @A, ubyte row @Y) clobbers(Y) -> ubyte @ A {
+	; ---- get the color in the screen color matrix at the given location
+	%asm  {{
+		pha
+		tya
+		asl  a
+		tay
+		lda  setclr._colorrows+1,y
+		sta  _mod+2
+		pla
+		clc
+		adc  setclr._colorrows,y
+		sta  _mod+1
+		bcc  _mod
+		inc  _mod+2
+_mod		lda  $ffff		; modified
+		rts
+	}}
+}
+
+sub  setcc  (ubyte column, ubyte row, ubyte char, ubyte charcolor)  {
+	; ---- set char+color at the given position on the screen
+	%asm {{
+		lda  row
+		asl  a
+		tay
+		lda  setchr._screenrows+1,y
+		sta  _charmod+2
+		adc  #$d4
+		sta  _colormod+2
+		lda  setchr._screenrows,y
+		clc
+		adc  column
+		sta  _charmod+1
+		sta  _colormod+1
+		bcc  +
+		inc  _charmod+2
+		inc  _colormod+2
+		lda  char
+_charmod	sta  $ffff		; modified
+		lda  charcolor
+_colormod	sta  $ffff		; modified
+		rts
+	}}
+}
+
+asmsub  plot  (ubyte col @ Y, ubyte row @ A) clobbers(A) {
+	; ---- safe wrapper around PLOT kernel routine, to save the X register.
+	%asm  {{
+		stx  P8ZP_SCRATCH_REG
+		tax
+		clc
+		jsr  c64.PLOT
+		ldx  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub width() clobbers(X,Y) -> ubyte @A {
+    ; -- returns the text screen width (number of columns)
+    %asm {{
+        jsr  c64.SCREEN
+        txa
+        rts
+    }}
+}
+
+asmsub height() clobbers(X, Y) -> ubyte @A {
+    ; -- returns the text screen height (number of rows)
+    %asm {{
+        jsr  c64.SCREEN
+        tya
+        rts
+    }}
+}
+
+}
@@ -0,0 +1,361 @@
+; Prog8 definitions for number conversions routines.
+;
+; Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+;
+; indent format: TABS, size=8
+
+
+conv {
+
+; ----- number conversions to decimal strings
+
+asmsub  ubyte2decimal  (ubyte value @ A) -> ubyte @ Y, ubyte @ A, ubyte @ X  {
+	; ---- A to decimal string in Y/A/X  (100s in Y, 10s in A, 1s in X)
+    %asm {{
+        ldy  #uword2decimal.ASCII_0_OFFSET
+        bne  uword2decimal.hex_try200
+        rts
+	}}
+}
+
+asmsub  uword2decimal  (uword value @ AY) -> ubyte @Y, ubyte @A, ubyte @X  {
+    ;  ---- convert 16 bit uword in A/Y to decimal
+    ;  output in uword2decimal.decTenThousands, decThousands, decHundreds, decTens, decOnes
+    ;  (these are terminated by a zero byte so they can be easily printed)
+    ;  also returns Y = 100's, A = 10's, X = 1's
+
+    %asm {{
+
+;Convert 16 bit Hex to Decimal (0-65535) Rev 2
+;By Omegamatrix    Further optimizations by tepples
+; routine from http://forums.nesdev.com/viewtopic.php?f=2&t=11341&start=15
+
+;HexToDec99
+; start in A
+; end with A = 10's, decOnes (also in X)
+
+;HexToDec255
+; start in A
+; end with Y = 100's, A = 10's, decOnes (also in X)
+
+;HexToDec999
+; start with A = high byte, Y = low byte
+; end with Y = 100's, A = 10's, decOnes (also in X)
+; requires 1 extra temp register on top of decOnes, could combine
+; these two if HexToDec65535 was eliminated...
+
+;HexToDec65535
+; start with A/Y (low/high) as 16 bit value
+; end with decTenThousand, decThousand, Y = 100's, A = 10's, decOnes (also in X)
+; (irmen: I store Y and A in decHundreds and decTens too, so all of it can be easily printed)
+
+
+ASCII_0_OFFSET 	= $30
+temp       	    = P8ZP_SCRATCH_B1	; byte in zeropage
+hexHigh      	= P8ZP_SCRATCH_W1	; byte in zeropage
+hexLow       	= P8ZP_SCRATCH_W1+1	; byte in zeropage
+
+
+HexToDec65535; SUBROUTINE
+    sty    hexHigh               ;3  @9
+    sta    hexLow                ;3  @12
+    tya
+    tax                          ;2  @14
+    lsr    a                     ;2  @16
+    lsr    a                     ;2  @18   integer divide 1024 (result 0-63)
+
+    cpx    #$A7                  ;2  @20   account for overflow of multiplying 24 from 43,000 ($A7F8) onward,
+    adc    #1                    ;2  @22   we can just round it to $A700, and the divide by 1024 is fine...
+
+    ;at this point we have a number 1-65 that we have to times by 24,
+    ;add to original sum, and Mod 1024 to get a remainder 0-999
+
+
+    sta    temp                  ;3  @25
+    asl    a                     ;2  @27
+    adc    temp                  ;3  @30  x3
+    tay                          ;2  @32
+    lsr    a                     ;2  @34
+    lsr    a                     ;2  @36
+    lsr    a                     ;2  @38
+    lsr    a                     ;2  @40
+    lsr    a                     ;2  @42
+    tax                          ;2  @44
+    tya                          ;2  @46
+    asl    a                     ;2  @48
+    asl    a                     ;2  @50
+    asl    a                     ;2  @52
+    clc                          ;2  @54
+    adc    hexLow                ;3  @57
+    sta    hexLow                ;3  @60
+    txa                          ;2  @62
+    adc    hexHigh               ;3  @65
+    sta    hexHigh               ;3  @68
+    ror    a                     ;2  @70
+    lsr    a                     ;2  @72
+    tay                          ;2  @74    integer divide 1,000 (result 0-65)
+
+    lsr    a                     ;2  @76    split the 1,000 and 10,000 digit
+    tax                          ;2  @78
+    lda    ShiftedBcdTab,x       ;4  @82
+    tax                          ;2  @84
+    rol    a                     ;2  @86
+    and    #$0F                  ;2  @88
+    ora    #ASCII_0_OFFSET
+    sta    decThousands          ;3  @91
+    txa                          ;2  @93
+    lsr    a                     ;2  @95
+    lsr    a                     ;2  @97
+    lsr    a                     ;2  @99
+    ora    #ASCII_0_OFFSET
+    sta    decTenThousands       ;3  @102
+
+    lda    hexLow                ;3  @105
+    cpy    temp                  ;3  @108
+    bmi    _doSubtract           ;2³ @110/111
+    beq    _useZero               ;2³ @112/113
+    adc    #23 + 24              ;2  @114
+_doSubtract
+    sbc    #23                   ;2  @116
+    sta    hexLow                ;3  @119
+_useZero
+    lda    hexHigh               ;3  @122
+    sbc    #0                    ;2  @124
+
+Start100s
+    and    #$03                  ;2  @126
+    tax                          ;2  @128   0,1,2,3
+    cmp    #2                    ;2  @130
+    rol    a                     ;2  @132   0,2,5,7
+    ora    #ASCII_0_OFFSET
+    tay                          ;2  @134   Y = Hundreds digit
+
+    lda    hexLow                ;3  @137
+    adc    Mod100Tab,x           ;4  @141    adding remainder of 256, 512, and 256+512 (all mod 100)
+    bcs    hex_doSub200             ;2³ @143/144
+
+hex_try200
+    cmp    #200                  ;2  @145
+    bcc    hex_try100               ;2³ @147/148
+hex_doSub200
+    iny                          ;2  @149
+    iny                          ;2  @151
+    sbc    #200                  ;2  @153
+hex_try100
+    cmp    #100                  ;2  @155
+    bcc    HexToDec99            ;2³ @157/158
+    iny                          ;2  @159
+    sbc    #100                  ;2  @161
+
+HexToDec99; SUBROUTINE
+    lsr    a                     ;2  @163
+    tax                          ;2  @165
+    lda    ShiftedBcdTab,x       ;4  @169
+    tax                          ;2  @171
+    rol    a                     ;2  @173
+    and    #$0F                  ;2  @175
+    ora    #ASCII_0_OFFSET
+    sta    decOnes               ;3  @178
+    txa                          ;2  @180
+    lsr    a                     ;2  @182
+    lsr    a                     ;2  @184
+    lsr    a                     ;2  @186
+    ora    #ASCII_0_OFFSET
+
+    ; irmen: load X with ones, and store Y and A too, for easy printing afterwards
+    sty  decHundreds
+    sta  decTens
+    ldx  decOnes
+    rts                          ;6  @192   Y=hundreds, A = tens digit, X=ones digit
+
+
+HexToDec999; SUBROUTINE
+    sty    hexLow                ;3  @9
+    jmp    Start100s             ;3  @12
+
+Mod100Tab
+    .byte 0,56,12,56+12
+
+ShiftedBcdTab
+    .byte $00,$01,$02,$03,$04,$08,$09,$0A,$0B,$0C
+    .byte $10,$11,$12,$13,$14,$18,$19,$1A,$1B,$1C
+    .byte $20,$21,$22,$23,$24,$28,$29,$2A,$2B,$2C
+    .byte $30,$31,$32,$33,$34,$38,$39,$3A,$3B,$3C
+    .byte $40,$41,$42,$43,$44,$48,$49,$4A,$4B,$4C
+
+decTenThousands   	.byte  0
+decThousands    	.byte  0
+decHundreds		.byte  0
+decTens			.byte  0
+decOnes   		.byte  0
+			.byte  0		; zero-terminate the decimal output string
+
+    }}
+}
+
+
+; ----- utility functions ----
+
+
+asmsub  byte2decimal  (byte value @ A) -> ubyte @ Y, ubyte @ A, ubyte @ X  {
+	; ---- A (signed byte) to decimal string in Y/A/X  (100s in Y, 10s in A, 1s in X)
+	;      note: if the number is negative, you have to deal with the '-' yourself!
+	%asm {{
+		cmp  #0
+		bpl  +
+		eor  #255
+		clc
+		adc  #1
+		jmp  ubyte2decimal
+	}}
+}
+
+asmsub  ubyte2hex  (ubyte value @ A) -> ubyte @ A, ubyte @ Y  {
+	; ---- A to hex petscii string in AY (first hex char in A, second hex char in Y)
+	%asm {{
+		stx  P8ZP_SCRATCH_REG
+		pha
+		and  #$0f
+		tax
+		ldy  _hex_digits,x
+		pla
+		lsr  a
+		lsr  a
+		lsr  a
+		lsr  a
+		tax
+		lda  _hex_digits,x
+		ldx  P8ZP_SCRATCH_REG
+		rts
+
+_hex_digits	.text "0123456789abcdef"	; can probably be reused for other stuff as well
+	}}
+}
+
+asmsub  uword2hex  (uword value @ AY) clobbers(A,Y)  {
+	; ---- convert 16 bit uword in A/Y into 4-character hexadecimal string 'uword2hex.output' (0-terminated)
+	%asm {{
+		sta  P8ZP_SCRATCH_REG
+		tya
+		jsr  ubyte2hex
+		sta  output
+		sty  output+1
+		lda  P8ZP_SCRATCH_REG
+		jsr  ubyte2hex
+		sta  output+2
+		sty  output+3
+		rts
+output	.text  "0000", $00      ; 0-terminated output buffer (to make printing easier)
+	}}
+}
+
+asmsub str2uword(str string @ AY) -> uword @ AY {
+	; -- returns the unsigned word value of the string number argument in AY
+	;    the number may NOT be preceded by a + sign and may NOT contain spaces
+	;    (any non-digit character will terminate the number string that is parsed)
+	%asm {{
+_result = P8ZP_SCRATCH_W2
+		sta  _mod+1
+		sty  _mod+2
+		ldy  #0
+		sty  _result
+		sty  _result+1
+_mod		lda  $ffff,y		; modified
+		sec
+		sbc  #48
+		bpl  +
+_done		; return result
+		lda  _result
+		ldy  _result+1
+		rts
+		cmp  #10
+		bcs  _done
+		; add digit to result
+		pha
+		jsr  _result_times_10
+		pla
+		clc
+		adc  _result
+		sta  _result
+		bcc  +
+		inc  _result+1
+		iny
+		bne  _mod
+		; never reached
+
+_result_times_10     ; (W*4 + W)*2
+		lda  _result+1
+		sta  P8ZP_SCRATCH_REG
+		lda  _result
+		asl  a
+		rol  P8ZP_SCRATCH_REG
+		asl  a
+		rol  P8ZP_SCRATCH_REG
+		clc
+		adc  _result
+		sta  _result
+		lda  P8ZP_SCRATCH_REG
+		adc  _result+1
+		asl  _result
+		rol  a
+		sta  _result+1
+		rts
+	}}
+}
+
+asmsub str2word(str string @ AY) -> word @ AY {
+	; -- returns the signed word value of the string number argument in AY
+	;    the number may be preceded by a + or - sign but may NOT contain spaces
+	;    (any non-digit character will terminate the number string that is parsed)
+	%asm {{
+_result = P8ZP_SCRATCH_W2
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		ldy  #0
+		sty  _result
+		sty  _result+1
+		sty  _negative
+		lda  (P8ZP_SCRATCH_W1),y
+		cmp  #'+'
+		bne  +
+		iny
+		cmp  #'-'
+		bne  _parse
+		inc  _negative
+		iny
+_parse		lda  (P8ZP_SCRATCH_W1),y
+		sec
+		sbc  #48
+		bpl  _digit
+_done		; return result
+		lda  _negative
+		beq  +
+		sec
+		lda  #0
+		sbc  _result
+		sta  _result
+		lda  #0
+		sbc  _result+1
+		sta  _result+1
+		lda  _result
+		ldy  _result+1
+		rts
+_digit		cmp  #10
+		bcs  _done
+		; add digit to result
+		pha
+		jsr  str2uword._result_times_10
+		pla
+		clc
+		adc  _result
+		sta  _result
+		bcc  +
+		inc  _result+1
+		iny
+		bne  _parse
+		; never reached
+_negative	.byte  0
+	}}
+}
+
+}
@@ -0,0 +1,153 @@
+; Prog8 definitions for floating point handling on the CommanderX16
+;
+; Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+;
+; indent format: TABS, size=8
+
+%target cx16
+%option enable_floats
+
+floats {
+	; ---- this block contains C-64 floating point related functions ----
+
+        const float  PI     = 3.141592653589793
+        const float  TWOPI  = 6.283185307179586
+
+
+; ---- ROM float functions ----
+
+		; note: the fac1 and fac2 are working registers and take 6 bytes each,
+		; floats in memory  (and rom) are stored in 5-byte MFLPT packed format.
+
+; note: fac1/2 might get clobbered even if not mentioned in the function's name.
+; note: for subtraction and division, the left operand is in fac2, the right operand in fac1.
+
+romsub $fe00 = AYINT() clobbers(A,X,Y)          ; fac1-> signed word in 100-101 ($64-$65) MSB FIRST. (might throw ILLEGAL QUANTITY)
+
+; GIVAYF: signed word in Y/A (note different lsb/msb order) -> float in fac1
+; there is also floats.GIVUAYFAY - unsigned word in A/Y (lo/hi) to fac1
+; (tip: use GIVAYFAY to use A/Y input; lo/hi switched to normal order)
+romsub $fe03 = GIVAYF(ubyte lo @ Y, ubyte hi @ A) clobbers(A,X,Y)
+
+; fac1 -> unsigned word in Y/A (might throw ILLEGAL QUANTITY) (result also in $14/15)
+; (tip: use GETADRAY to get A/Y output; lo/hi switched to normal little endian order)
+romsub $fe06 = GETADR() clobbers(X) -> ubyte @ Y, ubyte @ A
+
+romsub $fe09 = FADDH() clobbers(A,X,Y)                      ; fac1 += 0.5, for rounding- call this before INT
+romsub $fe0c = FSUB(uword mflpt @ AY) clobbers(A,X,Y)       ; fac1 = mflpt from A/Y - fac1
+romsub $fe0f = FSUBT() clobbers(A,X,Y)                      ; fac1 = fac2-fac1   mind the order of the operands
+romsub $fe12 = FADD(uword mflpt @ AY) clobbers(A,X,Y)       ; fac1 += mflpt value from A/Y
+romsub $fe15 = FADDT() clobbers(A,X,Y)                      ; fac1 += fac2
+romsub $fe1b = ZEROFC() clobbers(A,X,Y)                     ; fac1 = 0
+romsub $fe1e = NORMAL() clobbers(A,X,Y)                     ; normalize fac1 (?)
+romsub $fe24 = LOG() clobbers(A,X,Y)                        ; fac1 = LN(fac1)  (natural log)
+romsub $fe27 = FMULT(uword mflpt @ AY) clobbers(A,X,Y)      ; fac1 *= mflpt value from A/Y
+romsub $fe2a = FMULTT() clobbers(A,X,Y)                     ; fac1 *= fac2
+romsub $fe33 = CONUPK(uword mflpt @ AY) clobbers(A,Y)       ; load mflpt value from memory  in A/Y into fac2
+romsub $fe36 = MUL10() clobbers(A,X,Y)                      ; fac1 *= 10
+romsub $fe3c = DIV10() clobbers(A,X,Y)                      ; fac1 /= 10 , CAUTION: result is always positive!
+romsub $fe3f = FDIV(uword mflpt @ AY) clobbers(A,X,Y)       ; fac1 = mflpt in A/Y / fac1  (remainder in fac2)
+romsub $fe42 = FDIVT() clobbers(A,X,Y)                      ; fac1 = fac2/fac1  (remainder in fac2)  mind the order of the operands
+
+romsub $fe48 = MOVFM(uword mflpt @ AY) clobbers(A,Y)        ; load mflpt value from memory  in A/Y into fac1
+romsub $fe4b = MOVMF(uword mflpt @ XY) clobbers(A,Y)        ; store fac1 to memory  X/Y as 5-byte mflpt
+romsub $fe4e = MOVFA() clobbers(A,X)                        ; copy fac2 to fac1
+romsub $fe51 = MOVAF() clobbers(A,X)                        ; copy fac1 to fac2  (rounded)
+romsub $fe54 = MOVEF() clobbers(A,X)                        ; copy fac1 to fac2
+romsub $fe5a = SIGN() -> ubyte @ A                          ; SIGN(fac1) to A, $ff, $0, $1 for negative, zero, positive
+romsub $fe5d = SGN() clobbers(A,X,Y)                        ; fac1 = SGN(fac1), result of SIGN (-1, 0 or 1)
+romsub $fe60 = FREADSA(byte value @ A) clobbers(A,X,Y)      ; 8 bit signed A -> float in fac1
+romsub $fe6c = ABS()                                        ; fac1 = ABS(fac1)
+romsub $fe6f = FCOMP(uword mflpt @ AY) clobbers(X,Y) -> ubyte @ A   ; A = compare fac1 to mflpt in A/Y, 0=equal 1=fac1 is greater, 255=fac1 is less than
+romsub $fe78 = INT() clobbers(A,X,Y)                        ; INT() truncates, use FADDH first to round instead of trunc
+romsub $fe7e = FINLOG(byte value @A) clobbers (A, X, Y)           ; fac1 += signed byte in A
+romsub $fe81 = FOUT() clobbers(X) -> uword @ AY             ; fac1 -> string, address returned in AY
+romsub $fe8a = SQR() clobbers(A,X,Y)                        ; fac1 = SQRT(fac1)
+romsub $fe8d = FPWRT() clobbers(A,X,Y)                      ; fac1 = fac2 ** fac1
+romsub $fe93 = NEGOP() clobbers(A)                          ; switch the sign of fac1
+romsub $fe96 = EXP() clobbers(A,X,Y)                        ; fac1 = EXP(fac1)  (e ** fac1)
+romsub $fe9f = RND2(byte value @A) clobbers(A,X,Y)                ; fac1 = RND(A) float random number generator
+romsub $fea2 = RND() clobbers(A,X,Y)                        ; fac1 = RND(fac1) float random number generator
+romsub $fea5 = COS() clobbers(A,X,Y)                        ; fac1 = COS(fac1)
+romsub $fea8 = SIN() clobbers(A,X,Y)                        ; fac1 = SIN(fac1)
+romsub $feab = TAN() clobbers(A,X,Y)                        ; fac1 = TAN(fac1)
+romsub $feae = ATN() clobbers(A,X,Y)                        ; fac1 = ATN(fac1)
+
+
+asmsub  GIVUAYFAY  (uword value @ AY) clobbers(A,X,Y)  {
+	; ---- unsigned 16 bit word in A/Y (lo/hi) to fac1
+	%asm {{
+        phx
+        sta  P8ZP_SCRATCH_REG
+        sty  P8ZP_SCRATCH_B1
+        tya
+        ldy  P8ZP_SCRATCH_REG
+        jsr  GIVAYF                 ; load it as signed... correct afterwards
+        lda  P8ZP_SCRATCH_B1
+	    bpl  +
+	    lda  #<_flt65536
+	    ldy  #>_flt65536
+	    jsr  FADD
+	    plx
+        rts
+_flt65536    .byte 145,0,0,0,0       ; 65536.0
+	}}
+}
+
+
+asmsub  GIVAYFAY  (uword value @ AY) clobbers(A,X,Y)  {
+	; ---- signed 16 bit word in A/Y (lo/hi) to float in fac1
+	%asm {{
+		sta  P8ZP_SCRATCH_REG
+		tya
+		ldy  P8ZP_SCRATCH_REG
+		jmp  GIVAYF		; this uses the inverse order, Y/A
+	}}
+}
+
+asmsub  FTOSWRDAY  () clobbers(X) -> uword @ AY  {
+	; ---- fac1 to signed word in A/Y
+	%asm {{
+		jsr  FTOSWORDYA	; note the inverse Y/A order
+		sta  P8ZP_SCRATCH_REG
+		tya
+		ldy  P8ZP_SCRATCH_REG
+		rts
+	}}
+}
+
+asmsub  GETADRAY  () clobbers(X) -> uword @ AY  {
+	; ---- fac1 to unsigned word in A/Y
+	%asm {{
+		jsr  GETADR		; this uses the inverse order, Y/A
+		sta  P8ZP_SCRATCH_B1
+		tya
+		ldy  P8ZP_SCRATCH_B1
+		rts
+	}}
+}
+
+sub  print_f  (float value) {
+	; ---- prints the floating point value (without a newline).
+	%asm {{
+		phx
+		lda  #<value
+		ldy  #>value
+		jsr  MOVFM		; load float into fac1
+		jsr  FOUT		; fac1 to string in A/Y
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		ldy  #0
+-		lda  (P8ZP_SCRATCH_W1),y
+		beq  +
+		jsr  c64.CHROUT
+		iny
+		bne  -
+		plx
+		rts
+	}}
+}
+
+%asminclude "library:c64/floats.asm", ""
+
+}
@@ -0,0 +1,156 @@
+%target cx16
+%import syslib
+
+; bitmap pixel graphics module for the CommanderX16
+; wraps the graphics functions that are in ROM.
+; only black/white monchrome 320x200 for now.
+
+graphics {
+    const uword WIDTH = 320
+    const ubyte HEIGHT = 200
+
+    sub enable_bitmap_mode() {
+        ; enable bitmap screen, erase it and set colors to black/white.
+        void cx16.screen_set_mode($80)
+        cx16.r0 = 0
+        cx16.GRAPH_init()
+        clear_screen(1, 0)
+    }
+
+    sub clear_screen(ubyte pixelcolor, ubyte bgcolor) {
+        cx16.GRAPH_set_colors(pixelcolor, pixelcolor, bgcolor)
+        cx16.GRAPH_clear()
+    }
+
+    sub line(uword @zp x1, ubyte @zp y1, uword @zp x2, ubyte @zp y2) {
+        cx16.r0 = x1
+        cx16.r1 = y1
+        cx16.r2 = x2
+        cx16.r3 = y2
+        cx16.GRAPH_draw_line()
+    }
+
+    sub circle(uword xcenter, ubyte ycenter, ubyte radius) {
+        ;cx16.r0 = xcenter - radius/2
+        ;cx16.r1 = ycenter - radius/2
+        ;cx16.r2 = radius*2
+        ;cx16.r3 = radius*2
+        ;cx16.GRAPH_draw_oval(false)          ; TODO  currently is not implemented on cx16, does a BRK
+
+        ; Midpoint algorithm
+        ubyte @zp xx = radius
+        ubyte @zp yy = 0
+        byte @zp decisionOver2 = 1-xx as byte
+
+        while xx>=yy {
+            cx16.r0 = xcenter + xx
+            cx16.r1 = ycenter + yy
+            cx16.FB_cursor_position()
+            cx16.FB_set_pixel(1)
+            cx16.r0 = xcenter - xx
+            cx16.FB_cursor_position()
+            cx16.FB_set_pixel(1)
+            cx16.r0 = xcenter + xx
+            cx16.r1 = ycenter - yy
+            cx16.FB_cursor_position()
+            cx16.FB_set_pixel(1)
+            cx16.r0 = xcenter - xx
+            cx16.FB_cursor_position()
+            cx16.FB_set_pixel(1)
+            cx16.r0 = xcenter + yy
+            cx16.r1 = ycenter + xx
+            cx16.FB_cursor_position()
+            cx16.FB_set_pixel(1)
+            cx16.r0 = xcenter - yy
+            cx16.FB_cursor_position()
+            cx16.FB_set_pixel(1)
+            cx16.r0 = xcenter + yy
+            cx16.r1 = ycenter - xx
+            cx16.FB_cursor_position()
+            cx16.FB_set_pixel(1)
+            cx16.r0 = xcenter - yy
+            cx16.FB_cursor_position()
+            cx16.FB_set_pixel(1)
+            yy++
+            if decisionOver2<=0 {
+                decisionOver2 += 2*yy+1
+            } else {
+                xx--
+                decisionOver2 += 2*(yy-xx)+1
+            }
+        }
+    }
+
+    sub disc(uword xcenter, ubyte ycenter, ubyte radius) {
+;        cx16.r0 = xcenter - radius/2
+;        cx16.r1 = ycenter - radius/2
+;        cx16.r2 = radius*2
+;        cx16.r3 = radius*2
+;        cx16.GRAPH_draw_oval(true)          ; TODO  currently is not implemented on cx16, does a BRK
+
+        ubyte xx = radius
+        ubyte yy = 0
+        byte decisionOver2 = 1-xx as byte
+
+        while xx>=yy {
+            ubyte ycenter_plus_yy = ycenter + yy
+            ubyte ycenter_min_yy = ycenter - yy
+            ubyte ycenter_plus_xx = ycenter + xx
+            ubyte ycenter_min_xx = ycenter - xx
+            uword @zp plotx
+
+            for plotx in xcenter to xcenter+xx {
+                cx16.r0 = plotx
+                cx16.r1 = ycenter_plus_yy
+                cx16.FB_cursor_position()
+                cx16.FB_set_pixel(1)
+                cx16.r1 = ycenter_min_yy
+                cx16.FB_cursor_position()
+                cx16.FB_set_pixel(1)
+            }
+            for plotx in xcenter-xx to xcenter-1 {
+                cx16.r0 = plotx
+                cx16.r1 = ycenter_plus_yy
+                cx16.FB_cursor_position()
+                cx16.FB_set_pixel(1)
+                cx16.r1 = ycenter_min_yy
+                cx16.FB_cursor_position()
+                cx16.FB_set_pixel(1)
+            }
+            for plotx in xcenter to xcenter+yy {
+                cx16.r0 = plotx
+                cx16.r1 = ycenter_plus_xx
+                cx16.FB_cursor_position()
+                cx16.FB_set_pixel(1)
+                cx16.r1 = ycenter_min_xx
+                cx16.FB_cursor_position()
+                cx16.FB_set_pixel(1)
+            }
+            for plotx in xcenter-yy to xcenter {
+                cx16.r0 = plotx
+                cx16.r1 = ycenter_plus_xx
+                cx16.FB_cursor_position()
+                cx16.FB_set_pixel(1)
+                cx16.r1 = ycenter_min_xx
+                cx16.FB_cursor_position()
+                cx16.FB_set_pixel(1)
+            }
+            yy++
+            if decisionOver2<=0
+                decisionOver2 += 2*yy+1
+            else {
+                xx--
+                decisionOver2 += 2*(yy-xx)+1
+            }
+        }
+    }
+
+    sub  plot(uword plotx, ubyte ploty) {
+        cx16.r0 = plotx
+        cx16.r1 = ploty
+        cx16.FB_cursor_position()
+        cx16.FB_set_pixel(1)
+    }
+}
+
+
@@ -0,0 +1,291 @@
+; Prog8 definitions for the CommanderX16
+; Including memory registers, I/O registers, Basic and Kernal subroutines.
+;
+; Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+;
+; indent format: TABS, size=8
+
+%target cx16
+
+
+c64 {
+
+; ---- kernal routines, these are the same as on the Commodore-64 (hence the same block name) ----
+
+; STROUT --> use screen.print
+; CLEARSCR -> use screen.clear_screen
+; HOMECRSR -> use screen.plot
+
+romsub $FF81 = CINT()  clobbers(A,X,Y)                           ; (alias: SCINIT) initialize screen editor and video chip
+romsub $FF84 = IOINIT()  clobbers(A, X)                          ; initialize I/O devices (CIA, SID, IRQ)
+romsub $FF87 = RAMTAS()  clobbers(A,X,Y)                         ; initialize RAM, tape buffer, screen
+romsub $FF8A = RESTOR()  clobbers(A,X,Y)                         ; restore default I/O vectors
+romsub $FF8D = VECTOR(uword userptr @ XY, ubyte dir @ Pc)  clobbers(A,Y)     ; read/set I/O vector table
+romsub $FF90 = SETMSG(ubyte value @ A)                          ; set Kernal message control flag
+romsub $FF93 = SECOND(ubyte address @ A)  clobbers(A)            ; (alias: LSTNSA) send secondary address after LISTEN
+romsub $FF96 = TKSA(ubyte address @ A)  clobbers(A)              ; (alias: TALKSA) send secondary address after TALK
+romsub $FF99 = MEMTOP(uword address @ XY, ubyte dir @ Pc) -> ubyte @A, uword @ XY     ; read/set top of memory  pointer, returns number of banks in A
+romsub $FF9C = MEMBOT(uword address @ XY, ubyte dir @ Pc) -> uword @ XY     ; read/set bottom of memory  pointer
+romsub $FF9F = SCNKEY()  clobbers(A,X,Y)                         ; scan the keyboard
+romsub $FFA2 = SETTMO(ubyte timeout @ A)                        ; set time-out flag for IEEE bus
+romsub $FFA5 = ACPTR() -> ubyte @ A                             ; (alias: IECIN) input byte from serial bus
+romsub $FFA8 = CIOUT(ubyte databyte @ A)                        ; (alias: IECOUT) output byte to serial bus
+romsub $FFAB = UNTLK()  clobbers(A)                              ; command serial bus device to UNTALK
+romsub $FFAE = UNLSN()  clobbers(A)                              ; command serial bus device to UNLISTEN
+romsub $FFB1 = LISTEN(ubyte device @ A)  clobbers(A)             ; command serial bus device to LISTEN
+romsub $FFB4 = TALK(ubyte device @ A)  clobbers(A)               ; command serial bus device to TALK
+romsub $FFB7 = READST() -> ubyte @ A                            ; read I/O status word
+romsub $FFBA = SETLFS(ubyte logical @ A, ubyte device @ X, ubyte address @ Y)   ; set logical file parameters
+romsub $FFBD = SETNAM(ubyte namelen @ A, str filename @ XY)     ; set filename parameters
+romsub $FFC0 = OPEN()  clobbers(A,X,Y)                           ; (via 794 ($31A)) open a logical file
+romsub $FFC3 = CLOSE(ubyte logical @ A)  clobbers(A,X,Y)         ; (via 796 ($31C)) close a logical file
+romsub $FFC6 = CHKIN(ubyte logical @ X)  clobbers(A,X)           ; (via 798 ($31E)) define an input channel
+romsub $FFC9 = CHKOUT(ubyte logical @ X)  clobbers(A,X)          ; (via 800 ($320)) define an output channel
+romsub $FFCC = CLRCHN()  clobbers(A,X)                           ; (via 802 ($322)) restore default devices
+romsub $FFCF = CHRIN()  clobbers(Y) -> ubyte @ A                 ; (via 804 ($324)) input a character (for keyboard, read a whole line from the screen) A=byte read.
+romsub $FFD2 = CHROUT(ubyte char @ A)                           ; (via 806 ($326)) output a character
+romsub $FFD5 = LOAD(ubyte verify @ A, uword address @ XY) -> ubyte @Pc, ubyte @ A, ubyte @ X, ubyte @ Y     ; (via 816 ($330)) load from device
+romsub $FFD8 = SAVE(ubyte zp_startaddr @ A, uword endaddr @ XY) -> ubyte @ Pc, ubyte @ A                    ; (via 818 ($332)) save to a device
+romsub $FFDB = SETTIM(ubyte low @ A, ubyte middle @ X, ubyte high @ Y)      ; set the software clock
+romsub $FFDE = RDTIM() -> ubyte @ A, ubyte @ X, ubyte @ Y       ; read the software clock
+romsub $FFE1 = STOP()  clobbers(A,X) -> ubyte @ Pz, ubyte @ Pc   ; (via 808 ($328)) check the STOP key
+romsub $FFE4 = GETIN()  clobbers(X,Y) -> ubyte @ A               ; (via 810 ($32A)) get a character
+romsub $FFE7 = CLALL()  clobbers(A,X)                            ; (via 812 ($32C)) close all files
+romsub $FFEA = UDTIM()  clobbers(A,X)                            ; update the software clock
+romsub $FFED = SCREEN() -> ubyte @ X, ubyte @ Y                 ; read number of screen rows and columns
+romsub $FFF0 = PLOT(ubyte col @ Y, ubyte row @ X, ubyte dir @ Pc) -> ubyte @ X, ubyte @ Y       ; read/set position of cursor on screen.  Use screen.plot for a 'safe' wrapper that preserves X.
+romsub $FFF3 = IOBASE() -> uword @ XY                           ; read base address of I/O devices
+
+}
+
+cx16 {
+
+; 65c02 hardware vectors:
+    &uword  NMI_VEC         = $FFFA     ; 6502 nmi vector, determined by the kernal if banked in
+    &uword  RESET_VEC       = $FFFC     ; 6502 reset vector, determined by the kernal if banked in
+    &uword  IRQ_VEC         = $FFFE     ; 6502 interrupt vector, determined by the kernal if banked in
+
+
+; the sixteen virtual 16-bit registers
+    &uword r0  = $0002
+    &uword r1  = $0004
+    &uword r2  = $0006
+    &uword r3  = $0008
+    &uword r4  = $000a
+    &uword r5  = $000c
+    &uword r6  = $000e
+    &uword r7  = $0010
+    &uword r8  = $0012
+    &uword r9  = $0014
+    &uword r10 = $0016
+    &uword r11 = $0018
+    &uword r12 = $001a
+    &uword r13 = $001c
+    &uword r14 = $001e
+    &uword r15 = $0020
+
+; VERA registers
+
+    const uword VERA_BASE = $9F20
+    &ubyte  VERA_ADDR_L   	  = VERA_BASE + $0000
+    &ubyte  VERA_ADDR_M   	  = VERA_BASE + $0001
+    &ubyte  VERA_ADDR_H   	  = VERA_BASE + $0002
+    &ubyte  VERA_DATA0        = VERA_BASE + $0003
+    &ubyte  VERA_DATA1        = VERA_BASE + $0004
+    &ubyte  VERA_CTRL         = VERA_BASE + $0005
+    &ubyte  VERA_IEN          = VERA_BASE + $0006
+    &ubyte  VERA_ISR          = VERA_BASE + $0007
+    &ubyte  VERA_IRQ_LINE_L   = VERA_BASE + $0008
+    &ubyte  VERA_DC_VIDEO     = VERA_BASE + $0009
+    &ubyte  VERA_DC_HSCALE    = VERA_BASE + $000A
+    &ubyte  VERA_DC_VSCALE    = VERA_BASE + $000B
+    &ubyte  VERA_DC_BORDER    = VERA_BASE + $000C
+    &ubyte  VERA_DC_HSTART    = VERA_BASE + $0009
+    &ubyte  VERA_DC_HSTOP     = VERA_BASE + $000A
+    &ubyte  VERA_DC_VSTART    = VERA_BASE + $000B
+    &ubyte  VERA_DC_VSTOP     = VERA_BASE + $000C
+    &ubyte  VERA_L0_CONFIG    = VERA_BASE + $000D
+    &ubyte  VERA_L0_MAPBASE   = VERA_BASE + $000E
+    &ubyte  VERA_L0_TILEBASE  = VERA_BASE + $000F
+    &ubyte  VERA_L0_HSCROLL_L = VERA_BASE + $0010
+    &ubyte  VERA_L0_HSCROLL_H = VERA_BASE + $0011
+    &ubyte  VERA_L0_VSCROLL_L = VERA_BASE + $0012
+    &ubyte  VERA_L0_VSCROLL_H = VERA_BASE + $0013
+    &ubyte  VERA_L1_CONFIG    = VERA_BASE + $0014
+    &ubyte  VERA_L1_MAPBASE   = VERA_BASE + $0015
+    &ubyte  VERA_L1_TILEBASE  = VERA_BASE + $0016
+    &ubyte  VERA_L1_HSCROLL_L = VERA_BASE + $0017
+    &ubyte  VERA_L1_HSCROLL_H = VERA_BASE + $0018
+    &ubyte  VERA_L1_VSCROLL_L = VERA_BASE + $0019
+    &ubyte  VERA_L1_VSCROLL_H = VERA_BASE + $001A
+    &ubyte  VERA_AUDIO_CTRL   = VERA_BASE + $001B
+    &ubyte  VERA_AUDIO_RATE   = VERA_BASE + $001C
+    &ubyte  VERA_AUDIO_DATA   = VERA_BASE + $001D
+    &ubyte  VERA_SPI_DATA     = VERA_BASE + $001E
+    &ubyte  VERA_SPI_CTRL     = VERA_BASE + $001F
+; VERA_PSG_BASE     = $1F9C0
+; VERA_PALETTE_BASE = $1FA00
+; VERA_SPRITES_BASE = $1FC00
+
+; I/O
+
+    const uword  via1  = $9f60                  ;VIA 6522 #1
+    &ubyte  d1prb	= via1+0
+    &ubyte  d1pra	= via1+1
+    &ubyte  d1ddrb	= via1+2
+    &ubyte  d1ddra	= via1+3
+    &ubyte  d1t1l	= via1+4
+    &ubyte  d1t1h	= via1+5
+    &ubyte  d1t1ll	= via1+6
+    &ubyte  d1t1lh	= via1+7
+    &ubyte  d1t2l	= via1+8
+    &ubyte  d1t2h	= via1+9
+    &ubyte  d1sr	= via1+10
+    &ubyte  d1acr	= via1+11
+    &ubyte  d1pcr	= via1+12
+    &ubyte  d1ifr	= via1+13
+    &ubyte  d1ier	= via1+14
+    &ubyte  d1ora	= via1+15
+
+    const uword  via2  = $9f70                  ;VIA 6522 #2
+    &ubyte  d2prb	=via2+0
+    &ubyte  d2pra	=via2+1
+    &ubyte  d2ddrb	=via2+2
+    &ubyte  d2ddra	=via2+3
+    &ubyte  d2t1l	=via2+4
+    &ubyte  d2t1h	=via2+5
+    &ubyte  d2t1ll	=via2+6
+    &ubyte  d2t1lh	=via2+7
+    &ubyte  d2t2l	=via2+8
+    &ubyte  d2t2h	=via2+9
+    &ubyte  d2sr	=via2+10
+    &ubyte  d2acr	=via2+11
+    &ubyte  d2pcr	=via2+12
+    &ubyte  d2ifr	=via2+13
+    &ubyte  d2ier	=via2+14
+    &ubyte  d2ora	=via2+15
+
+
+; ---- Commander X-16 additions on top of C64 kernal routines ----
+; spelling of the names is taken from the Commander X-16 rom sources
+
+; TODO specify the correct clobbers for alle these functions, for simplicity all 3 regs are marked clobbered atm
+
+; supported C128 additions
+romsub $ff4a = close_all()  clobbers(A,X,Y)
+romsub $ff59 = lkupla()  clobbers(A,X,Y)
+romsub $ff5c = lkupsa()  clobbers(A,X,Y)
+romsub $ff5f = screen_set_mode(ubyte mode @A)  clobbers(A, X, Y) -> ubyte @Pc
+romsub $ff62 = screen_set_charset(ubyte charset @A, uword charsetptr @XY)  clobbers(A,X,Y)      ; incompatible with C128  dlchr()
+romsub $ff65 = pfkey()  clobbers(A,X,Y)
+romsub $ff6e = jsrfar()  clobbers(A,X,Y)
+romsub $ff74 = fetch()  clobbers(A,X,Y)
+romsub $ff77 = stash()  clobbers(A,X,Y)
+romsub $ff7a = cmpare()  clobbers(A,X,Y)
+romsub $ff7d = primm()  clobbers(A,X,Y)
+
+; X16 additions
+romsub $ff44 = macptr()  clobbers(A,X,Y)
+romsub $ff47 = enter_basic(ubyte cold_or_warm @Pc)  clobbers(A,X,Y)
+romsub $ff68 = mouse_config(ubyte shape @A, ubyte scale @X)  clobbers (A, X, Y)
+romsub $ff6b = mouse_get(ubyte zpdataptr @X)  clobbers(A)
+romsub $ff71 = mouse_scan()  clobbers(A, X, Y)
+romsub $ff53 = joystick_scan()  clobbers(A, X, Y)
+romsub $ff56 = joystick_get(ubyte joynr @A) -> ubyte @A, ubyte @X, ubyte @Y
+romsub $ff4d = clock_set_date_time()  clobbers(A, X, Y)      ; args: r0, r1, r2, r3L
+romsub $ff50 = clock_get_date_time()  clobbers(A)            ; outout args: r0, r1, r2, r3L
+
+; high level graphics & fonts
+romsub $ff20 = GRAPH_init()  clobbers(A,X,Y)           ; uses vectors=r0
+romsub $ff23 = GRAPH_clear()  clobbers(A,X,Y)
+romsub $ff26 = GRAPH_set_window()  clobbers(A,X,Y)      ; uses x=r0, y=r1, width=r2, height=r3
+romsub $ff29 = GRAPH_set_colors(ubyte stroke @A, ubyte fill @X, ubyte background @Y)  clobbers (A,X,Y)
+romsub $ff2c = GRAPH_draw_line()  clobbers(A,X,Y)       ; uses x1=r0, y1=r1, x2=r2, y2=r3
+romsub $ff2f = GRAPH_draw_rect(ubyte fill @Pc)  clobbers(A,X,Y)   ; uses x=r0, y=r1, width=r2, height=r3, cornerradius=r4
+romsub $ff32 = GRAPH_move_rect()  clobbers(A,X,Y)       ; uses sx=r0, sy=r1, tx=r2, ty=r3, width=r4, height=r5
+romsub $ff35 = GRAPH_draw_oval(ubyte fill @Pc)  clobbers(A,X,Y)       ; uses x=r0, y=r1, width=r2, height=r3
+romsub $ff38 = GRAPH_draw_image()  clobbers(A,X,Y)      ; uses x=r0, y=r1, ptr=r2, width=r3, height=r4
+romsub $ff3b = GRAPH_set_font()  clobbers(A,X,Y)         ; uses ptr=r0
+romsub $ff3e = GRAPH_get_char_size(ubyte baseline @A, ubyte width @X, ubyte height_or_style @Y, ubyte is_control @Pc)  clobbers(A,X,Y)
+romsub $ff41 = GRAPH_put_char(ubyte char @A)  clobbers(A,X,Y)   ; uses x=r0, y=r1
+
+; framebuffer
+romsub $fef6 = FB_init()  clobbers(A,X,Y)
+romsub $fef9 = FB_get_info()  clobbers(X,Y) -> byte @A    ; also outputs width=r0, height=r1
+romsub $fefc = FB_set_palette(ubyte index @A, ubyte bytecount @X)  clobbers(A,X,Y)      ; also uses pointer=r0
+romsub $feff = FB_cursor_position()  clobbers(A,X,Y)    ; uses x=r0, y=r1
+romsub $ff02 = FB_cursor_next_line()  clobbers(A,X,Y)   ; uses x=r0
+romsub $ff05 = FB_get_pixel()  clobbers(X,Y) -> ubyte @A
+romsub $ff08 = FB_get_pixels()  clobbers(A,X,Y)         ; uses ptr=r0, count=r1
+romsub $ff0b = FB_set_pixel(ubyte color @A)  clobbers(A,X,Y)
+romsub $ff0e = FB_set_pixels()  clobbers(A,X,Y)         ; uses ptr=r0, count=r1
+romsub $ff11 = FB_set_8_pixels(ubyte pattern @A, ubyte color @X)  clobbers(A,X,Y)
+romsub $ff14 = FB_set_8_pixels_opaque(ubyte pattern @A, ubyte color1 @X, ubyte color2 @Y)  clobbers(A,X,Y)  ; also uses mask=r0L
+romsub $ff17 = FB_fill_pixels(ubyte color @A)  clobbers(A,X,Y)   ; also uses count=r0, step=r1
+romsub $ff1a = FB_filter_pixels()  clobbers(A,X,Y)      ; uses ptr=r0, count=r1
+romsub $ff1d = FB_move_pixels()  clobbers(A,X,Y)        ; uses sx=r0, sy=r1, tx=r2, ty=r3, count=r4
+
+; misc
+romsub $fef0 = sprite_set_image(ubyte number @A, ubyte width @X, ubyte height @Y, ubyte apply_mask @Pc)  clobbers(A,X,Y) -> ubyte @Pc  ; also uses pixels=r0, mask=r1, bpp=r2L
+romsub $fef3 = sprite_set_position(ubyte number @A)  clobbers(A,X,Y)  ; also uses x=r0 and y=r1
+romsub $fee4 = memory_fill(ubyte value @A)  clobbers(A,X,Y)      ; uses address=r0, num_bytes=r1
+romsub $fee7 = memory_copy()  clobbers(A,X,Y)                    ; uses source=r0, target=r1, num_bytes=r2
+romsub $feea = memory_crc()  clobbers(A,X,Y)                     ; uses address=r0, num_bytes=r1     result->r2
+romsub $feed = memory_decompress()  clobbers(A,X,Y)              ; uses input=r0, output=r1     result->r1
+romsub $fedb = console_init()  clobbers(A,X,Y)           ; uses x=r0, y=r1, width=r2, height=r3
+romsub $fede = console_put_char(ubyte char @A, ubyte wrapping @Pc)  clobbers(A,X,Y)
+romsub $fee1 = console_get_char()  clobbers(X,Y) -> ubyte @A
+romsub $fed8 = console_put_image()  clobbers(A,X,Y)      ; uses ptr=r0, width=r1, height=r2
+romsub $fed5 = console_set_paging_message()  clobbers(A,X,Y)     ; uses messageptr=r0
+romsub $fed2 = kbdbuf_put(ubyte key @A)  clobbers(A,X,Y)
+romsub $fecf = entropy_get() -> ubyte @A, ubyte @X, ubyte @Y
+romsub $fecc = monitor()  clobbers(A,X,Y)
+
+
+
+; ---- end of kernal routines ----
+
+asmsub init_system()  {
+    ; Initializes the machine to a sane starting state.
+    ; Called automatically by the loader program logic.
+    %asm {{
+        sei
+        cld
+        ;stz  $00
+        ;stz  $01
+        ;stz  d1prb      ; select rom bank 0
+        lda  #$80
+        sta  VERA_CTRL
+        jsr  c64.IOINIT
+        jsr  c64.RESTOR
+        jsr  c64.CINT
+        lda  #$90       ; black
+        jsr  c64.CHROUT
+        lda  #1         ; swap fg/bg
+        jsr  c64.CHROUT
+        lda  #$9e       ; yellow
+        jsr  c64.CHROUT
+        lda  #147       ; clear screen
+        jsr  c64.CHROUT
+        lda  #0
+        tax
+        tay
+        clc
+        clv
+        cli
+        rts
+    }}
+}
+
+asmsub  reset_system()  {
+    ; Soft-reset the system back to Basic prompt.
+    %asm {{
+        sei
+        lda  #14
+        sta  $01
+        stz  cx16.d1prb         ; bank the kernal in
+        jmp  (cx16.RESET_VEC)
+    }}
+}
+
+}
@@ -0,0 +1,696 @@
+; Prog8 definitions for the Text I/O and Screen routines for the CommanderX16
+;
+; Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+;
+; indent format: TABS, size=8
+
+%target cx16
+%import syslib
+%import conv
+
+
+txt {
+
+const ubyte DEFAULT_WIDTH = 80
+const ubyte DEFAULT_HEIGHT = 60
+
+
+sub  clear_screen() {
+    clear_screenchars(' ')
+}
+
+asmsub  fill_screen (ubyte char @ A, ubyte color @ Y) clobbers(A)  {
+	; ---- fill the character screen with the given fill character and character color.
+	%asm {{
+	    sty  _ly+1
+        phx
+        pha
+        jsr  c64.SCREEN             ; get dimensions in X/Y
+        txa
+        lsr  a
+        lsr  a
+        sta  _lx+1
+        stz  cx16.VERA_CTRL
+        lda  #%00010000
+        sta  cx16.VERA_ADDR_H       ; enable auto increment by 1, bank 0.
+        stz  cx16.VERA_ADDR_L       ; start at (0,0)
+        stz  cx16.VERA_ADDR_M
+        pla
+_lx     ldx  #0                     ; modified
+        phy
+_ly     ldy  #1                     ; modified
+-       sta  cx16.VERA_DATA0
+        sty  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        sty  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        sty  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        sty  cx16.VERA_DATA0
+        dex
+        bne  -
+        ply
+        dey
+        beq  +
+        stz  cx16.VERA_ADDR_L
+        inc  cx16.VERA_ADDR_M       ; next line
+        bra  _lx
+       plx
+        rts
+        }}
+}
+
+asmsub  clear_screenchars (ubyte char @ A) clobbers(Y)  {
+	; ---- clear the character screen with the given fill character (leaves colors)
+	;      (assumes screen matrix is at the default address)
+	%asm {{
+        phx
+        pha
+        jsr  c64.SCREEN             ; get dimensions in X/Y
+        txa
+        lsr  a
+        lsr  a
+        sta  _lx+1
+        stz  cx16.VERA_CTRL
+        lda  #%00100000
+        sta  cx16.VERA_ADDR_H       ; enable auto increment by 2, bank 0.
+        stz  cx16.VERA_ADDR_L       ; start at (0,0)
+        stz  cx16.VERA_ADDR_M
+        pla
+_lx     ldx  #0                     ; modified
+-       sta  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        dex
+        bne  -
+        dey
+        beq  +
+        stz  cx16.VERA_ADDR_L
+        inc  cx16.VERA_ADDR_M       ; next line
+        bra  _lx
+       plx
+        rts
+        }}
+}
+
+asmsub  clear_screencolors (ubyte color @ A) clobbers(Y)  {
+	; ---- clear the character screen colors with the given color (leaves characters).
+	;      (assumes color matrix is at the default address)
+	%asm {{
+        phx
+        sta  _la+1
+        jsr  c64.SCREEN             ; get dimensions in X/Y
+        txa
+        lsr  a
+        lsr  a
+        sta  _lx+1
+        stz  cx16.VERA_CTRL
+        lda  #%00100000
+        sta  cx16.VERA_ADDR_H       ; enable auto increment by 2, bank 0.
+        lda  #1
+        sta  cx16.VERA_ADDR_L       ; start at (1,0)
+        stz  cx16.VERA_ADDR_M
+_lx     ldx  #0                     ; modified
+_la     lda  #0                     ; modified
+-       sta  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA0
+        dex
+        bne  -
+        dey
+        beq  +
+        lda  #1
+        sta  cx16.VERA_ADDR_L
+        inc  cx16.VERA_ADDR_M       ; next line
+        bra  _lx
+       plx
+        rts
+        }}
+}
+
+
+ubyte[16] color_to_charcode = [$90,$05,$1c,$9f,$9c,$1e,$1f,$9e,$81,$95,$96,$97,$98,$99,$9a,$9b]
+
+sub color (ubyte txtcol) {
+    c64.CHROUT(color_to_charcode[txtcol & 15])
+}
+
+sub color2 (ubyte txtcol, ubyte bgcol) {
+    c64.CHROUT(color_to_charcode[bgcol & 15])
+    c64.CHROUT(1)       ; switch fg and bg colors
+    c64.CHROUT(color_to_charcode[txtcol & 15])
+}
+
+sub lowercase() {
+    cx16.screen_set_charset(3, 0)  ; lowercase charset
+}
+
+sub uppercase() {
+    cx16.screen_set_charset(2, 0)  ; uppercase charset
+}
+
+asmsub  scroll_left  (ubyte dummy @ Pc) clobbers(A, Y)  {
+	; ---- scroll the whole screen 1 character to the left
+	;      contents of the rightmost column are unchanged, you should clear/refill this yourself
+	;      Carry flag is a dummy on the cx16
+	%asm {{
+	    phx
+	    jsr  c64.SCREEN
+	    dex
+	    stx  _lx+1
+        dey
+        sty  P8ZP_SCRATCH_B1    ; number of rows to scroll
+
+_nextline
+        stz  cx16.VERA_CTRL     ; data port 0: source column
+        lda  #%00010000         ; auto increment 1
+        sta  cx16.VERA_ADDR_H
+        lda  #2
+        sta  cx16.VERA_ADDR_L   ; begin in column 1
+        ldy  P8ZP_SCRATCH_B1
+        sty  cx16.VERA_ADDR_M
+        lda  #1
+        sta  cx16.VERA_CTRL     ; data port 1: destination column
+        lda  #%00010000         ; auto increment 1
+        sta  cx16.VERA_ADDR_H
+        stz  cx16.VERA_ADDR_L
+        sty  cx16.VERA_ADDR_M
+
+_lx     ldx  #0                ; modified
+-       lda  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA1    ; copy char
+        lda  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA1    ; copy color
+        dex
+        bne  -
+        dec  P8ZP_SCRATCH_B1
+        bpl  _nextline
+
+        lda  #0
+        sta  cx16.VERA_CTRL
+	    plx
+	    rts
+	}}
+}
+
+asmsub  scroll_right  (ubyte dummy @ Pc) clobbers(A)  {
+	; ---- scroll the whole screen 1 character to the right
+	;      contents of the leftmost column are unchanged, you should clear/refill this yourself
+	;      Carry flag is a dummy on the cx16
+	%asm {{
+	    phx
+	    jsr  c64.SCREEN
+	    dex
+	    stx  _lx+1
+	    txa
+	    asl  a
+	    dea
+	    sta  _rcol+1
+	    ina
+	    ina
+	    sta  _rcol2+1
+        dey
+        sty  P8ZP_SCRATCH_B1    ; number of rows to scroll
+
+_nextline
+        stz  cx16.VERA_CTRL     ; data port 0: source column
+        lda  #%00011000         ; auto decrement 1
+        sta  cx16.VERA_ADDR_H
+_rcol   lda  #79*2-1             ; modified
+        sta  cx16.VERA_ADDR_L   ; begin in rightmost column minus one
+        ldy  P8ZP_SCRATCH_B1
+        sty  cx16.VERA_ADDR_M
+        lda  #1
+        sta  cx16.VERA_CTRL     ; data port 1: destination column
+        lda  #%00011000         ; auto decrement 1
+        sta  cx16.VERA_ADDR_H
+_rcol2  lda  #79*2+1            ; modified
+        sta  cx16.VERA_ADDR_L
+        sty  cx16.VERA_ADDR_M
+
+_lx     ldx  #0                 ; modified
+-       lda  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA1    ; copy char
+        lda  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA1    ; copy color
+        dex
+        bne  -
+        dec  P8ZP_SCRATCH_B1
+        bpl  _nextline
+
+        lda  #0
+        sta  cx16.VERA_CTRL
+	    plx
+	    rts
+	}}
+}
+
+asmsub  scroll_up  (ubyte dummy @ Pc) clobbers(A, Y)  {
+	; ---- scroll the whole screen 1 character up
+	;      contents of the bottom row are unchanged, you should refill/clear this yourself
+	;      Carry flag is a dummy on the cx16
+	%asm {{
+	    phx
+	    jsr  c64.SCREEN
+	    stx  _nextline+1
+	    dey
+        sty  P8ZP_SCRATCH_B1
+        stz  cx16.VERA_CTRL         ; data port 0 is source
+        lda  #1
+        sta  cx16.VERA_ADDR_M       ; start at second line
+        stz  cx16.VERA_ADDR_L
+        lda  #%00010000
+        sta  cx16.VERA_ADDR_H       ; enable auto increment by 1, bank 0.
+
+        lda  #1
+        sta  cx16.VERA_CTRL         ; data port 1 is destination
+        stz  cx16.VERA_ADDR_M       ; start at top line
+        stz  cx16.VERA_ADDR_L
+        lda  #%00010000
+        sta  cx16.VERA_ADDR_H       ; enable auto increment by 1, bank 0.
+
+_nextline
+        ldx  #80        ; modified
+-       lda  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA1        ; copy char
+        lda  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA1        ; copy color
+        dex
+        bne  -
+        dec  P8ZP_SCRATCH_B1
+        beq  +
+        stz  cx16.VERA_CTRL         ; data port 0
+        stz  cx16.VERA_ADDR_L
+        inc  cx16.VERA_ADDR_M
+        lda  #1
+        sta  cx16.VERA_CTRL         ; data port 1
+        stz  cx16.VERA_ADDR_L
+        inc  cx16.VERA_ADDR_M
+        bra  _nextline
+
+       lda  #0
+        sta  cx16.VERA_CTRL
+	    plx
+	    rts
+	}}
+}
+
+asmsub  scroll_down  (ubyte dummy @ Pc) clobbers(A, Y)  {
+	; ---- scroll the whole screen 1 character down
+	;      contents of the top row are unchanged, you should refill/clear this yourself
+	;      Carry flag is a dummy on the cx16
+	%asm {{
+	    phx
+	    jsr  c64.SCREEN
+	    stx  _nextline+1
+	    dey
+        sty  P8ZP_SCRATCH_B1
+        stz  cx16.VERA_CTRL         ; data port 0 is source
+        dey
+        sty  cx16.VERA_ADDR_M       ; start at line before bottom line
+        stz  cx16.VERA_ADDR_L
+        lda  #%00010000
+        sta  cx16.VERA_ADDR_H       ; enable auto increment by 1, bank 0.
+
+        lda  #1
+        sta  cx16.VERA_CTRL         ; data port 1 is destination
+        iny
+        sty  cx16.VERA_ADDR_M       ; start at bottom line
+        stz  cx16.VERA_ADDR_L
+        lda  #%00010000
+        sta  cx16.VERA_ADDR_H       ; enable auto increment by 1, bank 0.
+
+_nextline
+        ldx  #80        ; modified
+-       lda  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA1        ; copy char
+        lda  cx16.VERA_DATA0
+        sta  cx16.VERA_DATA1        ; copy color
+        dex
+        bne  -
+        dec  P8ZP_SCRATCH_B1
+        beq  +
+        stz  cx16.VERA_CTRL         ; data port 0
+        stz  cx16.VERA_ADDR_L
+        dec  cx16.VERA_ADDR_M
+        lda  #1
+        sta  cx16.VERA_CTRL         ; data port 1
+        stz  cx16.VERA_ADDR_L
+        dec  cx16.VERA_ADDR_M
+        bra  _nextline
+
+       lda  #0
+        sta  cx16.VERA_CTRL
+	    plx
+	    rts
+	}}
+}
+
+romsub $FFD2 = chrout(ubyte char @ A)    ; for consistency. You can also use c64.CHROUT directly ofcourse.
+
+asmsub  print (str text @ AY) clobbers(A,Y)  {
+	; ---- print null terminated string from A/Y
+	; note: the compiler contains an optimization that will replace
+	;       a call to this subroutine with a string argument of just one char,
+	;       by just one call to c64.CHROUT of that single char.
+	%asm {{
+		sta  P8ZP_SCRATCH_B1
+		sty  P8ZP_SCRATCH_REG
+		ldy  #0
+-		lda  (P8ZP_SCRATCH_B1),y
+		beq  +
+		jsr  c64.CHROUT
+		iny
+		bne  -
+		rts
+	}}
+}
+
+asmsub  print_ub0  (ubyte value @ A) clobbers(A,Y)  {
+	; ---- print the ubyte in A in decimal form, with left padding 0s (3 positions total)
+	%asm {{
+		phx
+		jsr  conv.ubyte2decimal
+		pha
+		tya
+		jsr  c64.CHROUT
+		pla
+		jsr  c64.CHROUT
+		txa
+		jsr  c64.CHROUT
+		plx
+		rts
+	}}
+}
+
+asmsub  print_ub  (ubyte value @ A) clobbers(A,Y)  {
+	; ---- print the ubyte in A in decimal form, without left padding 0s
+	%asm {{
+		phx
+		jsr  conv.ubyte2decimal
+_print_byte_digits
+		pha
+		cpy  #'0'
+		beq  +
+		tya
+		jsr  c64.CHROUT
+		pla
+		jsr  c64.CHROUT
+		jmp  _ones
+       pla
+        cmp  #'0'
+        beq  _ones
+        jsr  c64.CHROUT
+_ones   txa
+		jsr  c64.CHROUT
+		plx
+		rts
+	}}
+}
+
+asmsub  print_b  (byte value @ A) clobbers(A,Y)  {
+	; ---- print the byte in A in decimal form, without left padding 0s
+	%asm {{
+		phx
+		pha
+		cmp  #0
+		bpl  +
+		lda  #'-'
+		jsr  c64.CHROUT
+		pla
+		jsr  conv.byte2decimal
+		jmp  print_ub._print_byte_digits
+	}}
+}
+
+asmsub  print_ubhex  (ubyte value @ A, ubyte prefix @ Pc) clobbers(A,Y)  {
+	; ---- print the ubyte in A in hex form (if Carry is set, a radix prefix '$' is printed as well)
+	%asm {{
+		phx
+		bcc  +
+		pha
+		lda  #'$'
+		jsr  c64.CHROUT
+		pla
+		jsr  conv.ubyte2hex
+		jsr  c64.CHROUT
+		tya
+		jsr  c64.CHROUT
+		plx
+		rts
+	}}
+}
+
+asmsub  print_ubbin  (ubyte value @ A, ubyte prefix @ Pc) clobbers(A,Y)  {
+	; ---- print the ubyte in A in binary form (if Carry is set, a radix prefix '%' is printed as well)
+	%asm {{
+		phx
+		sta  P8ZP_SCRATCH_B1
+		bcc  +
+		lda  #'%'
+		jsr  c64.CHROUT
+		ldy  #8
+-		lda  #'0'
+		asl  P8ZP_SCRATCH_B1
+		bcc  +
+		lda  #'1'
+		jsr  c64.CHROUT
+		dey
+		bne  -
+		plx
+		rts
+	}}
+}
+
+asmsub  print_uwbin  (uword value @ AY, ubyte prefix @ Pc) clobbers(A,Y)  {
+	; ---- print the uword in A/Y in binary form (if Carry is set, a radix prefix '%' is printed as well)
+	%asm {{
+		pha
+		tya
+		jsr  print_ubbin
+		pla
+		clc
+		jmp  print_ubbin
+	}}
+}
+
+asmsub  print_uwhex  (uword value @ AY, ubyte prefix @ Pc) clobbers(A,Y)  {
+	; ---- print the uword in A/Y in hexadecimal form (4 digits)
+	;      (if Carry is set, a radix prefix '$' is printed as well)
+	%asm {{
+		pha
+		tya
+		jsr  print_ubhex
+		pla
+		clc
+		jmp  print_ubhex
+	}}
+}
+
+asmsub  print_uw0  (uword value @ AY) clobbers(A,Y)  {
+	; ---- print the uword in A/Y in decimal form, with left padding 0s (5 positions total)
+	%asm {{
+	    phx
+		jsr  conv.uword2decimal
+		ldy  #0
+-		lda  conv.uword2decimal.decTenThousands,y
+        beq  +
+		jsr  c64.CHROUT
+		iny
+		bne  -
+		plx
+		rts
+	}}
+}
+
+asmsub  print_uw  (uword value @ AY) clobbers(A,Y)  {
+	; ---- print the uword in A/Y in decimal form, without left padding 0s
+	%asm {{
+	    phx
+		jsr  conv.uword2decimal
+		plx
+		ldy  #0
+-		lda  conv.uword2decimal.decTenThousands,y
+		beq  _allzero
+		cmp  #'0'
+		bne  _gotdigit
+		iny
+		bne  -
+
+_gotdigit
+		jsr  c64.CHROUT
+		iny
+		lda  conv.uword2decimal.decTenThousands,y
+		bne  _gotdigit
+		rts
+_allzero
+        lda  #'0'
+        jmp  c64.CHROUT
+	}}
+}
+
+asmsub  print_w  (word value @ AY) clobbers(A,Y)  {
+	; ---- print the (signed) word in A/Y in decimal form, without left padding 0's
+	%asm {{
+		cpy  #0
+		bpl  +
+		pha
+		lda  #'-'
+		jsr  c64.CHROUT
+		tya
+		eor  #255
+		tay
+		pla
+		eor  #255
+		clc
+		adc  #1
+		bcc  +
+		iny
+		jmp  print_uw
+	}}
+}
+
+asmsub  input_chars  (uword buffer @ AY) clobbers(A) -> ubyte @ Y  {
+	; ---- Input a string (max. 80 chars) from the keyboard. Returns length in Y. (string is terminated with a 0 byte as well)
+	;      It assumes the keyboard is selected as I/O channel!
+
+	%asm {{
+		sta  P8ZP_SCRATCH_W1
+		sty  P8ZP_SCRATCH_W1+1
+		ldy  #0				; char counter = 0
+-		jsr  c64.CHRIN
+		cmp  #$0d			; return (ascii 13) pressed?
+		beq  +				; yes, end.
+		sta  (P8ZP_SCRATCH_W1),y	; else store char in buffer
+		iny
+		bne  -
+		lda  #0
+		sta  (P8ZP_SCRATCH_W1),y	; finish string with 0 byte
+		rts
+
+	}}
+}
+
+asmsub  setchr  (ubyte col @X, ubyte row @Y, ubyte character @A) clobbers(A)  {
+	; ---- sets the character in the screen matrix at the given position
+	%asm {{
+		pha
+		txa
+		asl  a
+        stz  cx16.VERA_CTRL
+		stz  cx16.VERA_ADDR_H
+		sta  cx16.VERA_ADDR_L
+		sty  cx16.VERA_ADDR_M
+		pla
+        sta  cx16.VERA_DATA0
+		rts
+	}}
+}
+
+asmsub  getchr  (ubyte col @A, ubyte row @Y) -> ubyte @ A {
+	; ---- get the character in the screen matrix at the given location
+	%asm  {{
+		asl  a
+        stz  cx16.VERA_CTRL
+		stz  cx16.VERA_ADDR_H
+		sta  cx16.VERA_ADDR_L
+		sty  cx16.VERA_ADDR_M
+        lda  cx16.VERA_DATA0
+		rts
+	}}
+}
+
+asmsub  setclr  (ubyte col @X, ubyte row @Y, ubyte color @A) clobbers(A)  {
+	; ---- set the color in A on the screen matrix at the given position
+	%asm {{
+		pha
+		txa
+		asl  a
+		ina
+        stz  cx16.VERA_CTRL
+		stz  cx16.VERA_ADDR_H
+		sta  cx16.VERA_ADDR_L
+		sty  cx16.VERA_ADDR_M
+		pla
+        sta  cx16.VERA_DATA0
+		rts
+	}}
+}
+
+asmsub  getclr  (ubyte col @A, ubyte row @Y) -> ubyte @ A {
+	; ---- get the color in the screen color matrix at the given location
+	%asm  {{
+		asl  a
+		ina
+        stz  cx16.VERA_CTRL
+		stz  cx16.VERA_ADDR_H
+		sta  cx16.VERA_ADDR_L
+		sty  cx16.VERA_ADDR_M
+        lda  cx16.VERA_DATA0
+		rts
+	}}
+}
+
+sub  setcc  (ubyte column, ubyte row, ubyte char, ubyte charcolor)  {
+	; ---- set char+color at the given position on the screen
+	%asm {{
+	    phx
+		lda  column
+		asl  a
+		tax
+		ldy  row
+		lda  charcolor
+		and  #$0f
+	    sta  P8ZP_SCRATCH_B1
+        stz  cx16.VERA_CTRL
+        stz  cx16.VERA_ADDR_H
+        stx  cx16.VERA_ADDR_L
+        sty  cx16.VERA_ADDR_M
+        lda  char
+        sta  cx16.VERA_DATA0
+        inx
+        stz  cx16.VERA_ADDR_H
+        stx  cx16.VERA_ADDR_L
+        sty  cx16.VERA_ADDR_M
+        lda  cx16.VERA_DATA0
+        and  #$f0
+        ora  P8ZP_SCRATCH_B1
+        sta  cx16.VERA_DATA0
+		plx
+		rts
+    }}
+}
+
+asmsub  plot  (ubyte col @ Y, ubyte row @ A) clobbers(A) {
+	; ---- safe wrapper around PLOT kernel routine, to save the X register.
+	%asm  {{
+		phx
+		tax
+		clc
+		jsr  c64.PLOT
+		plx
+		rts
+	}}
+}
+
+asmsub width() clobbers(X,Y) -> ubyte @A {
+    ; -- returns the text screen width (number of columns)
+    %asm {{
+        jsr  c64.SCREEN
+        txa
+        rts
+    }}
+}
+
+asmsub height() clobbers(X, Y) -> ubyte @A {
+    ; -- returns the text screen height (number of rows)
+    %asm {{
+        jsr  c64.SCREEN
+        tya
+        rts
+    }}
+}
+
+}
@@ -4,8 +4,6 @@
 ;
 ; indent format: TABS, size=8

-%import c64lib
-
 math {
 	%asminclude "library:math.asm", ""
 }
@@ -4,8 +4,6 @@
 ;
 ; indent format: TABS, size=8

-%import c64lib
-
 prog8_lib {
 	%asminclude "library:prog8lib.asm", ""
 }
@@ -1 +1 @@
-1.81
+4.3
@@ -4,13 +4,10 @@ import kotlinx.cli.*
 import prog8.ast.base.AstException
 import prog8.compiler.CompilationResult
 import prog8.compiler.compileProgram
+import prog8.compiler.target.C64Target
+import prog8.compiler.target.Cx16Target
 import prog8.compiler.target.CompilationTarget
-import prog8.compiler.target.c64.C64MachineDefinition
-import prog8.compiler.target.c64.Petscii
-import prog8.compiler.target.c64.codegen.AsmGen
 import prog8.parser.ParsingFailedError
-import prog8.vm.astvm.AstVm
-import java.io.IOException
 import java.nio.file.FileSystems
 import java.nio.file.Path
 import java.nio.file.StandardWatchEventKinds
@@ -36,13 +33,13 @@ fun pathFrom(stringPath: String, vararg rest: String): Path  = FileSystems.getDe

 private fun compileMain(args: Array<String>) {
    val cli = CommandLineInterface("prog8compiler")
-    val startEmulator by cli.flagArgument("-emu", "auto-start the Vice C-64 emulator after successful compilation")
+    val startEmulator by cli.flagArgument("-emu", "auto-start emulator after successful compilation")
    val outputDir by cli.flagValueArgument("-out", "directory", "directory for output files instead of current directory", ".")
    val dontWriteAssembly by cli.flagArgument("-noasm", "don't create assembly code")
    val dontOptimize by cli.flagArgument("-noopt", "don't perform any optimizations")
-    val launchSimulator by cli.flagArgument("-sim", "launch the builtin execution simulator after compilation")
    val watchMode by cli.flagArgument("-watch", "continuous compilation mode (watches for file changes), greatly increases compilation speed")
-    val compilationTarget by cli.flagValueArgument("-target", "compilertarget", "target output of the compiler, currently only 'c64' (C64 6502 assembly) available", "c64")
+    val compilationTarget by cli.flagValueArgument("-target", "compilertarget",
+            "target output of the compiler, currently '${C64Target.name}' and '${Cx16Target.name}' available", C64Target.name)
    val moduleFiles by cli.positionalArgumentsList("modules", "main module file(s) to compile", minArgs = 1)

    try {
@@ -51,26 +48,6 @@ private fun compileMain(args: Array<String>) {
        exitProcess(1)
    }

-    when(compilationTarget) {
-        "c64" -> {
-            with(CompilationTarget) {
-                name = "c64"
-                machine = C64MachineDefinition
-                encodeString = { str, altEncoding ->
-                    if(altEncoding) Petscii.encodeScreencode(str, true) else Petscii.encodePetscii(str, true)
-                }
-                decodeString = { bytes, altEncoding ->
-                    if(altEncoding) Petscii.decodeScreencode(bytes, true) else Petscii.decodePetscii(bytes, true)
-                }
-                asmGenerator = ::AsmGen
-            }
-        }
-        else -> {
-            System.err.println("invalid compilation target")
-            exitProcess(1)
-        }
-    }
-
    val outputPath = pathFrom(outputDir)
    if(!outputPath.toFile().isDirectory) {
        System.err.println("Output path doesn't exist")
@@ -85,7 +62,7 @@ private fun compileMain(args: Array<String>) {
            println("Continuous watch mode active. Main module: $filepath")

            try {
-                val compilationResult = compileProgram(filepath, !dontOptimize, !dontWriteAssembly, outputDir=outputPath)
+                val compilationResult = compileProgram(filepath, !dontOptimize, !dontWriteAssembly, compilationTarget, outputPath)
                println("Imported files (now watching:)")
                for (importedFile in compilationResult.importedFiles) {
                    print("  ")
@@ -110,7 +87,7 @@ private fun compileMain(args: Array<String>) {
            val filepath = pathFrom(filepathRaw).normalize()
            val compilationResult: CompilationResult
            try {
-                compilationResult = compileProgram(filepath, !dontOptimize, !dontWriteAssembly, outputDir=outputPath)
+                compilationResult = compileProgram(filepath, !dontOptimize, !dontWriteAssembly, compilationTarget, outputPath)
                if(!compilationResult.success)
                    exitProcess(1)
            } catch (x: ParsingFailedError) {
@@ -119,36 +96,11 @@ private fun compileMain(args: Array<String>) {
                exitProcess(1)
            }

-            if (launchSimulator) {
-//                val c64 = razorvine.c64emu.C64Machine("C64 emulator launched from Prog8 compiler")
-//                c64.cpu.addBreakpoint(0xea31) { cpu, address ->
-//                    println("zz")
-//                    Cpu6502.BreakpointResultAction()
-//                }
-//                c64.start()
-                println("\nLaunching AST-based simulator...")
-                val vm = AstVm(compilationResult.programAst, compilationTarget)
-                vm.run()
-            }
-
            if (startEmulator) {
                if (compilationResult.programName.isEmpty())
                    println("\nCan't start emulator because no program was assembled.")
                else if(startEmulator) {
-                    for(emulator in listOf("x64sc", "x64")) {
-                        println("\nStarting C-64 emulator $emulator...")
-                        val cmdline = listOf(emulator, "-silent", "-moncommands", "${compilationResult.programName}.vice-mon-list",
-                                "-autostartprgmode", "1", "-autostart-warp", "-autostart", compilationResult.programName + ".prg")
-                        val processb = ProcessBuilder(cmdline).inheritIO()
-                        val process: Process
-                        try {
-                            process=processb.start()
-                        } catch(x: IOException) {
-                            continue  // try the next emulator executable
-                        }
-                        process.waitFor()
-                        break
-                    }
+                    CompilationTarget.instance.machine.launchEmulator(compilationResult.programName)
                }
            }
        }
@@ -102,6 +102,12 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
    }

    override fun visit(decl: VarDecl) {
+
+        // if the vardecl is a parameter of a subroutine, don't output it again
+        val paramNames = (decl.definingScope() as? Subroutine)?.parameters?.map { it.name }
+        if(paramNames!=null && decl.name in paramNames)
+            return
+
        when(decl.type) {
            VarDeclType.VAR -> {}
            VarDeclType.CONST -> output("const ")
@@ -134,7 +140,7 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
                            param.second.stack -> "stack"
                            param.second.registerOrPair!=null -> param.second.registerOrPair.toString()
                            param.second.statusflag!=null -> param.second.statusflag.toString()
-                            else -> "?????1"
+                            else -> "?????"
                        }
                output("${datatypeString(param.first.type)} ${param.first.name} @$reg")
                if(param.first!==subroutine.parameters.last())
@@ -177,8 +183,6 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):

    private fun outputStatements(statements: List<Statement>) {
        for(stmt in statements) {
-            if(stmt is VarDecl && stmt.autogeneratedDontRemove)
-                continue    // skip autogenerated decls (to avoid generating a newline)
            outputi("")
            stmt.accept(this)
            output("\n")
@@ -283,20 +287,19 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
    }

    override fun visit(assignment: Assignment) {
-        if(assignment is VariableInitializationAssignment) {
-            val targetVar = assignment.target.identifier?.targetVarDecl(program.namespace)
-            if(targetVar?.struct != null) {
-                // skip STRUCT init assignments
-                return
-            }
-        }
-
-        assignment.target.accept(this)
-        if (assignment.aug_op != null)
-            output(" ${assignment.aug_op} ")
-        else
+        val binExpr = assignment.value as? BinaryExpression
+        if(binExpr!=null && binExpr.left isSameAs assignment.target
+                && binExpr.operator !in setOf("and", "or", "xor")
+                && binExpr.operator !in comparisonOperators) {
+            // we only support the inplace assignments of the form A = A <operator> <value>
+            assignment.target.accept(this)
+            output(" ${binExpr.operator}= ")
+            binExpr.right.accept(this)
+        } else {
+            assignment.target.accept(this)
            output(" = ")
-        assignment.value.accept(this)
+            assignment.value.accept(this)
+        }
    }

    override fun visit(postIncrDecr: PostIncrDecr) {
@@ -304,20 +307,13 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
        output(postIncrDecr.operator)
    }

-    override fun visit(contStmt: Continue) {
-        output("continue")
-    }
-
    override fun visit(breakStmt: Break) {
        output("break")
    }

    override fun visit(forLoop: ForLoop) {
        output("for ")
-        if(forLoop.loopRegister!=null)
-            output(forLoop.loopRegister.toString())
-        else
-            forLoop.loopVar!!.accept(this)
+        forLoop.loopVar.accept(this)
        output(" in ")
        forLoop.iterable.accept(this)
        output(" ")
@@ -331,16 +327,18 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
        whileLoop.body.accept(this)
    }

-    override fun visit(foreverLoop: ForeverLoop) {
-        output("forever ")
-        foreverLoop.body.accept(this)
-    }
-
    override fun visit(repeatLoop: RepeatLoop) {
        output("repeat ")
+        repeatLoop.iterations?.accept(this)
+        output(" ")
        repeatLoop.body.accept(this)
+    }
+
+    override fun visit(untilLoop: UntilLoop) {
+        output("do ")
+        untilLoop.body.accept(this)
        output(" until ")
-        repeatLoop.untilCondition.accept(this)
+        untilLoop.untilCondition.accept(this)
    }

    override fun visit(returnStmt: Return) {
@@ -356,12 +354,8 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
    }

    override fun visit(assignTarget: AssignTarget) {
-        if(assignTarget.register!=null)
-            output(assignTarget.register.toString())
-        else {
-            assignTarget.memoryAddress?.accept(this)
-            assignTarget.identifier?.accept(this)
-        }
+        assignTarget.memoryAddress?.accept(this)
+        assignTarget.identifier?.accept(this)
        assignTarget.arrayindexed?.accept(this)
    }

@@ -402,10 +396,6 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
        outputlni("}}")
    }

-    override fun visit(registerExpr: RegisterExpr) {
-        output(registerExpr.register.toString())
-    }
-
    override fun visit(builtinFunctionStatementPlaceholder: BuiltinFunctionStatementPlaceholder) {
        output(builtinFunctionStatementPlaceholder.name)
    }
@@ -439,12 +429,4 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
            whenChoice.statements.accept(this)
        outputln("")
    }
-
-    override fun visit(structLv: StructLiteralValue) {
-        outputListMembers(structLv.values.asSequence(), '{', '}')
-    }
-
-    override fun visit(nopStatement: NopStatement) {
-        output("; NOP @ ${nopStatement.position}  $nopStatement")
-    }
 }
@@ -3,6 +3,8 @@ package prog8.ast
 import prog8.ast.base.*
 import prog8.ast.expressions.Expression
 import prog8.ast.expressions.IdentifierReference
+import prog8.ast.processing.AstWalker
+import prog8.ast.processing.IAstVisitor
 import prog8.ast.statements.*
 import prog8.functions.BuiltinFunctions
 import java.nio.file.Path
@@ -33,6 +35,8 @@ interface Node {
            return this
        throw FatalAstException("scope missing from $this")
    }
+
+    fun replaceChildNode(node: Node, replacement: Node)
 }

 interface IFunctionCall {
@@ -48,32 +52,31 @@ interface INameScope {

    fun linkParents(parent: Node)

-    fun subScopes(): Map<String, INameScope> {
-        val subscopes = mutableMapOf<String, INameScope>()
+    fun subScope(name: String): INameScope? {
        for(stmt in statements) {
            when(stmt) {
                // NOTE: if other nodes are introduced that are a scope, or contain subscopes, they must be added here!
-                is ForLoop -> subscopes[stmt.body.name] = stmt.body
-                is RepeatLoop -> subscopes[stmt.body.name] = stmt.body
-                is WhileLoop -> subscopes[stmt.body.name] = stmt.body
+                is ForLoop -> if(stmt.body.name==name) return stmt.body
+                is UntilLoop -> if(stmt.body.name==name) return stmt.body
+                is WhileLoop -> if(stmt.body.name==name) return stmt.body
                is BranchStatement -> {
-                    subscopes[stmt.truepart.name] = stmt.truepart
-                    if(stmt.elsepart.containsCodeOrVars())
-                        subscopes[stmt.elsepart.name] = stmt.elsepart
+                    if(stmt.truepart.name==name) return stmt.truepart
+                    if(stmt.elsepart.containsCodeOrVars() && stmt.elsepart.name==name) return stmt.elsepart
                }
                is IfStatement -> {
-                    subscopes[stmt.truepart.name] = stmt.truepart
-                    if(stmt.elsepart.containsCodeOrVars())
-                        subscopes[stmt.elsepart.name] = stmt.elsepart
+                    if(stmt.truepart.name==name) return stmt.truepart
+                    if(stmt.elsepart.containsCodeOrVars() && stmt.elsepart.name==name) return stmt.elsepart
                }
                is WhenStatement -> {
-                    stmt.choices.forEach { subscopes[it.statements.name] = it.statements }
+                    val scope = stmt.choices.firstOrNull { it.statements.name==name }
+                    if(scope!=null)
+                        return scope.statements
                }
-                is INameScope -> subscopes[stmt.name] = stmt
+                is INameScope -> if(stmt.name==name) return stmt
                else -> {}
            }
        }
-        return subscopes
+        return null
    }

    fun getLabelOrVariable(name: String): Statement? {
@@ -121,7 +124,7 @@ interface INameScope {
            for(module in localContext.definingModule().program.modules) {
                var scope: INameScope? = module
                for(name in scopedName.dropLast(1)) {
-                    scope = scope?.subScopes()?.get(name)
+                    scope = scope?.subScope(name)
                    if(scope==null)
                        break
                }
@@ -129,7 +132,7 @@ interface INameScope {
                    val result = scope.getLabelOrVariable(scopedName.last())
                    if(result!=null)
                        return result
-                    return scope.subScopes()[scopedName.last()] as Statement?
+                    return scope.subScope(scopedName.last()) as Statement?
                }
            }
            return null
@@ -141,7 +144,7 @@ interface INameScope {
                val result = localScope.getLabelOrVariable(scopedName[0])
                if (result != null)
                    return result
-                val subscope = localScope.subScopes()[scopedName[0]] as Statement?
+                val subscope = localScope.subScope(scopedName[0]) as Statement?
                if (subscope != null)
                    return subscope
                // not found in this scope, look one higher up
@@ -152,6 +155,7 @@ interface INameScope {
    }

    fun containsCodeOrVars() = statements.any { it !is Directive || it.directive == "%asminclude" || it.directive == "%asm"}
+    fun containsNoVars() = statements.all { it !is VarDecl }
    fun containsNoCodeNorVars() = !containsCodeOrVars()

    fun remove(stmt: Statement) {
@@ -171,10 +175,11 @@ interface INameScope {
                        find(it.truepart)
                        find(it.elsepart)
                    }
+                    is UntilLoop -> find(it.body)
                    is RepeatLoop -> find(it.body)
-                    is ForeverLoop -> find(it.body)
                    is WhileLoop -> find(it.body)
                    is WhenStatement -> it.choices.forEach { choice->find(choice.statements) }
+                    else -> { /* do nothing */ }
                }
            }
        }
@@ -182,6 +187,14 @@ interface INameScope {
        find(this)
        return result
    }
+
+    fun nextSibling(stmt: Statement): Statement? {
+        val nextIdx = statements.indexOfFirst { it===stmt } + 1
+        return if(nextIdx < statements.size)
+            statements[nextIdx]
+        else
+            null
+    }
 }

 interface IAssignable {
@@ -191,7 +204,7 @@ interface IAssignable {

 /*********** Everything starts from here, the Program; zero or more modules *************/

-class Program(val name: String, val modules: MutableList<Module>) {
+class Program(val name: String, val modules: MutableList<Module>): Node {
    val namespace = GlobalNamespace(modules)

    val definedLoadAddress: Int
@@ -206,11 +219,29 @@ class Program(val name: String, val modules: MutableList<Module>) {
        return if(mainBlocks.isEmpty()) {
            null
        } else {
-            mainBlocks[0].subScopes()["start"] as Subroutine?
+            mainBlocks[0].subScope("start") as Subroutine?
        }
    }

    fun allBlocks(): List<Block> = modules.flatMap { it.statements.filterIsInstance<Block>() }
+
+    override val position: Position = Position.DUMMY
+    override var parent: Node
+        get() = throw FatalAstException("program has no parent")
+        set(value) = throw FatalAstException("can't set parent of program")
+
+    override fun linkParents(parent: Node) {
+        modules.forEach {
+            it.linkParents(this)
+        }
+    }
+
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(node is Module && replacement is Module)
+        val idx = modules.indexOfFirst { it===node }
+        modules[idx] = replacement
+        replacement.parent = this
+    }
 }

 class Module(override val name: String,
@@ -218,6 +249,7 @@ class Module(override val name: String,
             override val position: Position,
             val isLibraryModule: Boolean,
             val source: Path) : Node, INameScope {
+
    override lateinit var parent: Node
    lateinit var program: Program
    val importedBy = mutableListOf<Module>()
@@ -231,10 +263,20 @@ class Module(override val name: String,
    }

    override fun definingScope(): INameScope = program.namespace
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(node is Statement && replacement is Statement)
+        val idx = statements.indexOfFirst { it===node }
+        statements[idx] = replacement
+        replacement.parent = this
+    }

    override fun toString() = "Module(name=$name, pos=$position, lib=$isLibraryModule)"
+
+    fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

+
 class GlobalNamespace(val modules: List<Module>): Node, INameScope {
    override val name = "<<<global>>>"
    override val position = Position("<<<global>>>", 0, 0, 0)
@@ -245,6 +287,10 @@ class GlobalNamespace(val modules: List<Module>): Node, INameScope {
        modules.forEach { it.linkParents(this) }
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        throw FatalAstException("cannot replace anything in the namespace")
+    }
+
    override fun lookup(scopedName: List<String>, localContext: Node): Statement? {
        if (scopedName.size == 1 && scopedName[0] in BuiltinFunctions) {
            // builtin functions always exist, return a dummy localContext for them
@@ -268,9 +314,9 @@ class GlobalNamespace(val modules: List<Module>): Node, INameScope {
        }
        // lookup something from the module.
        return when (val stmt = localContext.definingModule().lookup(scopedName, localContext)) {
-            is Label, is VarDecl, is Block, is Subroutine -> stmt
+            is Label, is VarDecl, is Block, is Subroutine, is StructDecl -> stmt
            null -> null
-            else -> throw SyntaxError("wrong identifier target: $stmt", stmt.position)
+            else -> throw SyntaxError("invalid identifier target type", stmt.position)
        }
    }
 }
@@ -30,7 +30,7 @@ private fun ParserRuleContext.toPosition() : Position {
    val customTokensource = this.start.tokenSource as? CustomLexer
    val filename =
            when {
-                customTokensource!=null -> customTokensource.modulePath.fileName.toString()
+                customTokensource!=null -> customTokensource.modulePath.toString()
                start.tokenSource.sourceName == IntStream.UNKNOWN_SOURCE_NAME -> "@internal@"
                else -> File(start.inputStream.sourceName).name
            }
@@ -161,14 +161,15 @@ private fun prog8Parser.StatementContext.toAst() : Statement {
    if(vardecl!=null) return vardecl

    assignment()?.let {
-        return Assignment(it.assign_target().toAst(), null, it.expression().toAst(), it.toPosition())
+        return Assignment(it.assign_target().toAst(), it.expression().toAst(), it.toPosition())
    }

    augassignment()?.let {
-        return Assignment(it.assign_target().toAst(),
-                it.operator.text,
-                it.expression().toAst(),
-                it.toPosition())
+        // replace A += X  with  A = A + X
+        val target = it.assign_target().toAst()
+        val oper = it.operator.text.substringBefore('=')
+        val expression = BinaryExpression(target.toExpression(), oper, it.expression().toAst(), it.expression().toPosition())
+        return Assignment(it.assign_target().toAst(), expression, it.toPosition())
    }

    postincrdecr()?.let {
@@ -205,21 +206,18 @@ private fun prog8Parser.StatementContext.toAst() : Statement {
    val forloop = forloop()?.toAst()
    if(forloop!=null) return forloop

-    val repeatloop = repeatloop()?.toAst()
-    if(repeatloop!=null) return repeatloop
+    val untilloop = untilloop()?.toAst()
+    if(untilloop!=null) return untilloop

    val whileloop = whileloop()?.toAst()
    if(whileloop!=null) return whileloop

-    val foreverloop = foreverloop()?.toAst()
-    if(foreverloop!=null) return foreverloop
+    val repeatloop = repeatloop()?.toAst()
+    if(repeatloop!=null) return repeatloop

    val breakstmt = breakstmt()?.toAst()
    if(breakstmt!=null) return breakstmt

-    val continuestmt = continuestmt()?.toAst()
-    if(continuestmt!=null) return continuestmt
-
    val whenstmt = whenstmt()?.toAst()
    if(whenstmt!=null) return whenstmt

@@ -247,7 +245,7 @@ private class AsmsubDecl(val name: String,
                         val returntypes: List<DataType>,
                         val asmParameterRegisters: List<RegisterOrStatusflag>,
                         val asmReturnvaluesRegisters: List<RegisterOrStatusflag>,
-                         val asmClobbers: Set<Register>)
+                         val asmClobbers: Set<CpuRegister>)

 private fun prog8Parser.Asmsub_declContext.toAst(): AsmsubDecl {
    val name = identifier().text
@@ -256,7 +254,7 @@ private fun prog8Parser.Asmsub_declContext.toAst(): AsmsubDecl {
    val clobbers = asmsub_clobbers()?.clobber()?.toAst() ?: emptySet()
    val normalParameters = params.map { SubroutineParameter(it.name, it.type, it.position) }
    val normalReturntypes = returns.map { it.type }
-    val paramRegisters = params.map { RegisterOrStatusflag(it.registerOrPair, it.statusflag, it.stack) }
+    val paramRegisters = params.map { RegisterOrStatusflag(it.registerOrPair, it.statusflag, false) }
    val returnRegisters = returns.map { RegisterOrStatusflag(it.registerOrPair, it.statusflag, it.stack) }
    return AsmsubDecl(name, normalParameters, normalReturntypes, paramRegisters, returnRegisters, clobbers)
 }
@@ -265,7 +263,7 @@ private class AsmSubroutineParameter(name: String,
                                     type: DataType,
                                     val registerOrPair: RegisterOrPair?,
                                     val statusflag: Statusflag?,
-                                     val stack: Boolean,
+                                     // TODO implement: val stack: Boolean,
                                     position: Position) : SubroutineParameter(name, type, position)

 private class AsmSubroutineReturn(val type: DataType,
@@ -274,24 +272,42 @@ private class AsmSubroutineReturn(val type: DataType,
                                  val stack: Boolean,
                                  val position: Position)

-private fun prog8Parser.ClobberContext.toAst(): Set<Register>
-        = this.register().asSequence().map { it.toAst() }.toSet()
-
 private fun prog8Parser.Asmsub_returnsContext.toAst(): List<AsmSubroutineReturn>
-        = asmsub_return().map { AsmSubroutineReturn(it.datatype().toAst(), it.registerorpair()?.toAst(), it.statusregister()?.toAst(), !it.stack?.text.isNullOrEmpty(), toPosition()) }
+        = asmsub_return().map {
+            val register = it.identifier()?.toAst()
+            var registerorpair: RegisterOrPair? = null
+            var statusregister: Statusflag? = null
+            if(register!=null) {
+                when (val name = register.nameInSource.single()) {
+                    in RegisterOrPair.names -> registerorpair = RegisterOrPair.valueOf(name)
+                    in Statusflag.names -> statusregister = Statusflag.valueOf(name)
+                    else -> throw FatalAstException("invalid register or status flag in $it")
+                }
+            }
+            AsmSubroutineReturn(
+                    it.datatype().toAst(),
+                    registerorpair,
+                    statusregister,
+                    !it.stack?.text.isNullOrEmpty(), toPosition())
+        }

 private fun prog8Parser.Asmsub_paramsContext.toAst(): List<AsmSubroutineParameter>
        = asmsub_param().map {
    val vardecl = it.vardecl()
    val datatype = vardecl.datatype()?.toAst() ?: DataType.STRUCT
-    AsmSubroutineParameter(vardecl.varname.text, datatype,
-            it.registerorpair()?.toAst(),
-            it.statusregister()?.toAst(),
-            !it.stack?.text.isNullOrEmpty(), toPosition())
+    val register = it.identifier()?.toAst()
+    var registerorpair: RegisterOrPair? = null
+    var statusregister: Statusflag? = null
+    if(register!=null) {
+        when (val name = register.nameInSource.single()) {
+            in RegisterOrPair.names -> registerorpair = RegisterOrPair.valueOf(name)
+            in Statusflag.names -> statusregister = Statusflag.valueOf(name)
+            else -> throw FatalAstException("invalid register or status flag '$name'")
+        }
+    }
+    AsmSubroutineParameter(vardecl.varname.text, datatype, registerorpair, statusregister, toPosition())
 }

-private fun prog8Parser.StatusregisterContext.toAst() = Statusflag.valueOf(text)
-
 private fun prog8Parser.Functioncall_stmtContext.toAst(): Statement {
    val void = this.VOID() != null
    val location = scoped_identifier().toAst()
@@ -350,23 +366,22 @@ private fun prog8Parser.Sub_paramsContext.toAst(): List<SubroutineParameter> =
        }

 private fun prog8Parser.Assign_targetContext.toAst() : AssignTarget {
-    val register = register()?.toAst()
    val identifier = scoped_identifier()
    return when {
-        register!=null -> AssignTarget(register, null, null, null, toPosition())
-        identifier!=null -> AssignTarget(null, identifier.toAst(), null, null, toPosition())
-        arrayindexed()!=null -> AssignTarget(null, null, arrayindexed().toAst(), null, toPosition())
-        directmemory()!=null -> AssignTarget(null, null, null, DirectMemoryWrite(directmemory().expression().toAst(), toPosition()), toPosition())
-        else -> AssignTarget(null, scoped_identifier()?.toAst(), null, null, toPosition())
+        identifier!=null -> AssignTarget(identifier.toAst(), null, null, toPosition())
+        arrayindexed()!=null -> AssignTarget(null, arrayindexed().toAst(), null, toPosition())
+        directmemory()!=null -> AssignTarget(null, null, DirectMemoryWrite(directmemory().expression().toAst(), toPosition()), toPosition())
+        else -> AssignTarget(scoped_identifier()?.toAst(), null, null, toPosition())
    }
 }

-private fun prog8Parser.RegisterContext.toAst() = Register.valueOf(text.toUpperCase())
+private fun prog8Parser.ClobberContext.toAst() : Set<CpuRegister> {
+    val names = this.identifier().map { it.toAst().nameInSource.single() }
+    return names.map { CpuRegister.valueOf(it) }.toSet()
+}

 private fun prog8Parser.DatatypeContext.toAst() = DataType.valueOf(text.toUpperCase())

-private fun prog8Parser.RegisterorpairContext.toAst() = RegisterOrPair.valueOf(text.toUpperCase())
-
 private fun prog8Parser.ArrayindexContext.toAst() : ArrayIndex =
        ArrayIndex(expression().toAst(), toPosition())

@@ -382,7 +397,7 @@ private fun prog8Parser.DirectiveargContext.toAst() : DirectiveArg {
 }

 private fun prog8Parser.IntegerliteralContext.toAst(): NumericLiteral {
-    fun makeLiteral(text: String, radix: Int, forceWord: Boolean): NumericLiteral {
+    fun makeLiteral(text: String, radix: Int): NumericLiteral {
        val integer: Int
        var datatype = DataType.UBYTE
        when (radix) {
@@ -420,14 +435,14 @@ private fun prog8Parser.IntegerliteralContext.toAst(): NumericLiteral {
            }
            else -> throw FatalAstException("invalid radix")
        }
-        return NumericLiteral(integer, if (forceWord) DataType.UWORD else datatype)
+        return NumericLiteral(integer, datatype)
    }
    val terminal: TerminalNode = children[0] as TerminalNode
    val integerPart = this.intpart.text
    return when (terminal.symbol.type) {
-        prog8Parser.DEC_INTEGER -> makeLiteral(integerPart, 10, wordsuffix()!=null)
-        prog8Parser.HEX_INTEGER -> makeLiteral(integerPart.substring(1), 16, wordsuffix()!=null)
-        prog8Parser.BIN_INTEGER -> makeLiteral(integerPart.substring(1), 2, wordsuffix()!=null)
+        prog8Parser.DEC_INTEGER -> makeLiteral(integerPart, 10)
+        prog8Parser.HEX_INTEGER -> makeLiteral(integerPart.substring(1), 16)
+        prog8Parser.BIN_INTEGER -> makeLiteral(integerPart.substring(1), 2)
        else -> throw FatalAstException(terminal.text)
    }
 }
@@ -456,7 +471,7 @@ private fun prog8Parser.ExpressionContext.toAst() : Expression {
                litval.charliteral()!=null -> {
                    try {
                        val cc=litval.charliteral()
-                        NumericLiteralValue(DataType.UBYTE, CompilationTarget.encodeString(
+                        NumericLiteralValue(DataType.UBYTE, CompilationTarget.instance.encodeString(
                                unescape(litval.charliteral().SINGLECHAR().text, litval.toPosition()),
                                litval.charliteral().ALT_STRING_ENCODING()!=null)[0], litval.toPosition())
                    } catch (ce: CharConversionException) {
@@ -469,18 +484,11 @@ private fun prog8Parser.ExpressionContext.toAst() : Expression {
                    // the ConstantFold takes care of that and converts the type if needed.
                    ArrayLiteralValue(InferredTypes.InferredType.unknown(), array, position = litval.toPosition())
                }
-                litval.structliteral()!=null -> {
-                    val values = litval.structliteral().expression().map { it.toAst() }
-                    StructLiteralValue(values, litval.toPosition())
-                }
                else -> throw FatalAstException("invalid parsed literal")
            }
        }
    }

-    if(register()!=null)
-        return RegisterExpr(register().toAst(), register().toPosition())
-
    if(scoped_identifier()!=null)
        return scoped_identifier().toAst()

@@ -572,19 +580,16 @@ private fun prog8Parser.Branch_stmtContext.toAst(): BranchStatement {
 private fun prog8Parser.BranchconditionContext.toAst() = BranchCondition.valueOf(text.substringAfter('_').toUpperCase())

 private fun prog8Parser.ForloopContext.toAst(): ForLoop {
-    val loopregister = register()?.toAst()
-    val loopvar = identifier()?.toAst()
+    val loopvar = identifier().toAst()
    val iterable = expression()!!.toAst()
    val scope =
            if(statement()!=null)
                AnonymousScope(mutableListOf(statement().toAst()), statement().toPosition())
            else
                AnonymousScope(statement_block().toAst(), statement_block().toPosition())
-    return ForLoop(loopregister, loopvar, iterable, scope, toPosition())
+    return ForLoop(loopvar, iterable, scope, toPosition())
 }

-private fun prog8Parser.ContinuestmtContext.toAst() = Continue(toPosition())
-
 private fun prog8Parser.BreakstmtContext.toAst() = Break(toPosition())

 private fun prog8Parser.WhileloopContext.toAst(): WhileLoop {
@@ -595,19 +600,20 @@ private fun prog8Parser.WhileloopContext.toAst(): WhileLoop {
    return WhileLoop(condition, scope, toPosition())
 }

-private fun prog8Parser.ForeverloopContext.toAst(): ForeverLoop {
+private fun prog8Parser.RepeatloopContext.toAst(): RepeatLoop {
+    val iterations = expression()?.toAst()
    val statements = statement_block()?.toAst() ?: mutableListOf(statement().toAst())
    val scope = AnonymousScope(statements, statement_block()?.toPosition()
            ?: statement().toPosition())
-    return ForeverLoop(scope, toPosition())
+    return RepeatLoop(iterations, scope, toPosition())
 }

-private fun prog8Parser.RepeatloopContext.toAst(): RepeatLoop {
+private fun prog8Parser.UntilloopContext.toAst(): UntilLoop {
    val untilCondition = expression().toAst()
    val statements = statement_block()?.toAst() ?: mutableListOf(statement().toAst())
    val scope = AnonymousScope(statements, statement_block()?.toPosition()
            ?: statement().toPosition())
-    return RepeatLoop(scope, untilCondition, toPosition())
+    return UntilLoop(scope, untilCondition, toPosition())
 }

 private fun prog8Parser.WhenstmtContext.toAst(): WhenStatement {
@@ -21,10 +21,9 @@ enum class DataType {
    STRUCT;             // pass by reference

    /**
-     * is the type assignable to the given other type?
+     * is the type assignable to the given other type (perhaps via a typecast) without loss of precision?
     */
    infix fun isAssignableTo(targetType: DataType) =
-            // what types are assignable to others without loss of precision?
            when(this) {
                UBYTE -> targetType in setOf(UBYTE, WORD, UWORD, FLOAT)
                BYTE -> targetType in setOf(BYTE, WORD, FLOAT)
@@ -57,14 +56,14 @@ enum class DataType {
        return when(this) {
            in ByteDatatypes -> 1
            in WordDatatypes -> 2
-            FLOAT -> CompilationTarget.machine.FLOAT_MEM_SIZE
-            in PassByReferenceDatatypes -> 2
+            FLOAT -> CompilationTarget.instance.machine.FLOAT_MEM_SIZE
+            in PassByReferenceDatatypes -> CompilationTarget.instance.machine.POINTER_MEM_SIZE
            else -> -9999999
        }
    }
 }

-enum class Register {
+enum class CpuRegister {
    A,
    X,
    Y
@@ -76,14 +75,23 @@ enum class RegisterOrPair {
    Y,
    AX,
    AY,
-    XY
+    XY;
+
+    companion object {
+        val names by lazy { values().map { it.toString()} }
+    }
+
 }       // only used in parameter and return value specs in asm subroutines

 enum class Statusflag {
    Pc,
    Pz,
    Pv,
-    Pn
+    Pn;
+
+    companion object {
+        val names by lazy { values().map { it.toString()} }
+    }
 }

 enum class BranchCondition {
@@ -150,8 +158,16 @@ object ParentSentinel : Node {
    override val position = Position("<<sentinel>>", 0, 0, 0)
    override var parent: Node = this
    override fun linkParents(parent: Node) {}
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        replacement.parent = this
+    }
 }

 data class Position(val file: String, val line: Int, val startCol: Int, val endCol: Int) {
    override fun toString(): String = "[$file: line $line col ${startCol+1}-${endCol+1}]"
+    fun toClickableStr(): String = "$file:$line:$startCol:"
+
+    companion object {
+        val DUMMY = Position("<dummy>", 0, 0, 0)
+    }
 }
@@ -8,13 +8,13 @@ class ErrorReporter {
        WARNING,
        ERROR
    }
-    private class CompilerMessage(val severity: MessageSeverity, val message: String, val position: Position?)
+    private class CompilerMessage(val severity: MessageSeverity, val message: String, val position: Position)

    private val messages = mutableListOf<CompilerMessage>()
    private val alreadyReportedMessages = mutableSetOf<String>()

-    fun err(msg: String, position: Position?) = messages.add(CompilerMessage(MessageSeverity.ERROR, msg, position))
-    fun warn(msg: String, position: Position?) = messages.add(CompilerMessage(MessageSeverity.WARNING, msg, position))
+    fun err(msg: String, position: Position) = messages.add(CompilerMessage(MessageSeverity.ERROR, msg, position))
+    fun warn(msg: String, position: Position) = messages.add(CompilerMessage(MessageSeverity.WARNING, msg, position))

    fun handle() {
        var numErrors = 0
@@ -24,7 +24,7 @@ class ErrorReporter {
                MessageSeverity.ERROR -> System.err.print("\u001b[91m")  // bright red
                MessageSeverity.WARNING -> System.err.print("\u001b[93m")  // bright yellow
            }
-            val msg = "${it.position} ${it.severity} ${it.message}".trim()
+            val msg = "${it.position.toClickableStr()} ${it.severity} ${it.message}".trim()
            if(msg !in alreadyReportedMessages) {
                System.err.println(msg)
                alreadyReportedMessages.add(msg)
@@ -2,16 +2,16 @@ package prog8.ast.base

 import prog8.ast.expressions.IdentifierReference

-class FatalAstException (override var message: String) : Exception(message)
+open class FatalAstException (override var message: String) : Exception(message)

 open class AstException (override var message: String) : Exception(message)

 open class SyntaxError(override var message: String, val position: Position) : AstException(message) {
-    override fun toString() = "$position Syntax error: $message"
+    override fun toString() = "${position.toClickableStr()} Syntax error: $message"
 }

 class ExpressionError(message: String, val position: Position) : AstException(message) {
-    override fun toString() = "$position Error: $message"
+    override fun toString() = "${position.toClickableStr()} Error: $message"
 }

 class UndefinedSymbolError(symbol: IdentifierReference)
@@ -4,17 +4,7 @@ import prog8.ast.Module
 import prog8.ast.Program
 import prog8.ast.processing.*
 import prog8.compiler.CompilationOptions
-import prog8.optimizer.FlattenAnonymousScopesAndRemoveNops
-
-
-// the name of the subroutine that should be called for every block to initialize its variables
-internal const val initvarsSubName="prog8_init_vars"
-
-
-internal fun Program.removeNopsFlattenAnonScopes() {
-    val flattener = FlattenAnonymousScopesAndRemoveNops()
-    flattener.visit(this)
-}
+import prog8.compiler.BeforeAsmGenerationAstChanger


 internal fun Program.checkValid(compilerOptions: CompilationOptions, errors: ErrorReporter) {
@@ -22,29 +12,33 @@ internal fun Program.checkValid(compilerOptions: CompilationOptions, errors: Err
    checker.visit(this)
 }

-
-internal fun Program.anonscopeVarsCleanup(errors: ErrorReporter) {
-    val mover = AnonymousScopeVarsCleanup(errors)
-    mover.visit(this)
+internal fun Program.processAstBeforeAsmGeneration(errors: ErrorReporter) {
+    val fixer = BeforeAsmGenerationAstChanger(this, errors)
+    fixer.visit(this)
+    fixer.applyModifications()
 }

-
 internal fun Program.reorderStatements() {
-    val initvalueCreator = VarInitValueAndAddressOfCreator(this)
-    initvalueCreator.visit(this)
-
-    val checker = StatementReorderer(this)
-    checker.visit(this)
+    val reorder = StatementReorderer(this)
+    reorder.visit(this)
+    reorder.applyModifications()
 }

 internal fun Program.addTypecasts(errors: ErrorReporter) {
    val caster = TypecastsAdder(this, errors)
    caster.visit(this)
+    caster.applyModifications()
 }

-internal fun Module.checkImportedValid(errors: ErrorReporter) {
-    val checker = ImportedModuleDirectiveRemover(errors)
-    checker.visit(this)
+internal fun Program.verifyFunctionArgTypes() {
+    val fixer = VerifyFunctionArgTypes(this)
+    fixer.visit(this)
+}
+
+internal fun Module.checkImportedValid() {
+    val imr = ImportedModuleDirectiveRemover()
+    imr.visit(this, this.parent)
+    imr.applyModifications()
 }

 internal fun Program.checkRecursion(errors: ErrorReporter) {
@@ -53,18 +47,24 @@ internal fun Program.checkRecursion(errors: ErrorReporter) {
    checker.processMessages(name)
 }

-
 internal fun Program.checkIdentifiers(errors: ErrorReporter) {
-    val checker = AstIdentifiersChecker(this, errors)
-    checker.visit(this)

-    if(modules.map {it.name}.toSet().size != modules.size) {
+    val checker2 = AstIdentifiersChecker(this, errors)
+    checker2.visit(this)
+
+    if(errors.isEmpty()) {
+        val transforms = AstVariousTransforms(this)
+        transforms.visit(this)
+        transforms.applyModifications()
+    }
+
+    if (modules.map { it.name }.toSet().size != modules.size) {
        throw FatalAstException("modules should all be unique")
    }
 }

-
-internal fun Program.makeForeverLoops() {
-    val checker = MakeForeverLoops()
-    checker.visit(this)
+internal fun Program.variousCleanups() {
+    val process = VariousCleanups()
+    process.visit(this)
+    process.applyModifications()
 }
@@ -3,11 +3,12 @@ package prog8.ast.expressions
 import prog8.ast.*
 import prog8.ast.antlr.escape
 import prog8.ast.base.*
-import prog8.ast.processing.IAstModifyingVisitor
+import prog8.ast.processing.AstWalker
 import prog8.ast.processing.IAstVisitor
 import prog8.ast.statements.*
 import prog8.compiler.target.CompilationTarget
 import prog8.functions.BuiltinFunctions
+import prog8.functions.CannotEvaluateException
 import prog8.functions.NotConstArgumentException
 import prog8.functions.builtinFunctionReturnType
 import java.util.*
@@ -15,34 +16,52 @@ import kotlin.math.abs


 val associativeOperators = setOf("+", "*", "&", "|", "^", "or", "and", "xor", "==", "!=")
+val comparisonOperators = setOf("==", "!=", "<", ">", "<=", ">=")


 sealed class Expression: Node {
    abstract fun constValue(program: Program): NumericLiteralValue?
-    abstract fun accept(visitor: IAstModifyingVisitor): Expression
    abstract fun accept(visitor: IAstVisitor)
-    abstract fun referencesIdentifiers(vararg name: String): Boolean     // todo: remove this and add identifier usage tracking into CallGraph instead
+    abstract fun accept(visitor: AstWalker, parent: Node)
+    abstract fun referencesIdentifiers(vararg name: String): Boolean
    abstract fun inferType(program: Program): InferredTypes.InferredType

+    infix fun isSameAs(assigntarget: AssignTarget) = assigntarget.isSameAs(this)
+
    infix fun isSameAs(other: Expression): Boolean {
        if(this===other)
            return true
-        when(this) {
-            is RegisterExpr ->
-                return (other is RegisterExpr && other.register==register)
+        return when(this) {
            is IdentifierReference ->
-                return (other is IdentifierReference && other.nameInSource==nameInSource)
+                (other is IdentifierReference && other.nameInSource==nameInSource)
            is PrefixExpression ->
-                return (other is PrefixExpression && other.operator==operator && other.expression isSameAs expression)
+                (other is PrefixExpression && other.operator==operator && other.expression isSameAs expression)
            is BinaryExpression ->
-                return (other is BinaryExpression && other.operator==operator
+                (other is BinaryExpression && other.operator==operator
                        && other.left isSameAs left
                        && other.right isSameAs right)
            is ArrayIndexedExpression -> {
-                return (other is ArrayIndexedExpression && other.identifier.nameInSource == identifier.nameInSource
+                (other is ArrayIndexedExpression && other.identifier.nameInSource == identifier.nameInSource
                        && other.arrayspec.index isSameAs arrayspec.index)
            }
-            else -> return other==this
+            is DirectMemoryRead -> {
+                (other is DirectMemoryRead && other.addressExpression isSameAs addressExpression)
+            }
+            is TypecastExpression -> {
+                (other is TypecastExpression && other.implicit==implicit && other.type==type && other.expression isSameAs expression)
+            }
+            is AddressOf -> {
+                (other is AddressOf && other.identifier.nameInSource == identifier.nameInSource)
+            }
+            is RangeExpr -> {
+                (other is RangeExpr && other.from==from && other.to==to && other.step==step)
+            }
+            is FunctionCall -> {
+                (other is FunctionCall && other.target.nameInSource == target.nameInSource
+                        && other.args.size == args.size
+                        && other.args.zip(args).all { it.first isSameAs it.second } )
+            }
+            else -> other==this
        }
    }
 }
@@ -56,9 +75,16 @@ class PrefixExpression(val operator: String, var expression: Expression, overrid
        expression.linkParents(this)
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(node === expression && replacement is Expression)
+        expression = replacement
+        replacement.parent = this
+    }
+
    override fun constValue(program: Program): NumericLiteralValue? = null
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun referencesIdentifiers(vararg name: String) = expression.referencesIdentifiers(*name)
    override fun inferType(program: Program): InferredTypes.InferredType {
        val inferred = expression.inferType(program)
@@ -96,6 +122,16 @@ class BinaryExpression(var left: Expression, var operator: String, var right: Ex
        right.linkParents(this)
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression)
+        when {
+            node===left -> left = replacement
+            node===right -> right = replacement
+            else -> throw FatalAstException("invalid replace, no child $node")
+        }
+        replacement.parent = this
+    }
+
    override fun toString(): String {
        return "[$left $operator $right]"
    }
@@ -103,8 +139,9 @@ class BinaryExpression(var left: Expression, var operator: String, var right: Ex
    // binary expression should actually have been optimized away into a single value, before const value was requested...
    override fun constValue(program: Program): NumericLiteralValue? = null

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun referencesIdentifiers(vararg name: String) = left.referencesIdentifiers(*name) || right.referencesIdentifiers(*name)
    override fun inferType(program: Program): InferredTypes.InferredType {
        val leftDt = left.inferType(program)
@@ -205,9 +242,19 @@ class ArrayIndexedExpression(var identifier: IdentifierReference,
        arrayspec.linkParents(this)
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===identifier -> identifier = replacement as IdentifierReference
+            node===arrayspec.index -> arrayspec.index = replacement as Expression
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    override fun constValue(program: Program): NumericLiteralValue? = null
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun referencesIdentifiers(vararg name: String) = identifier.referencesIdentifiers(*name)

    override fun inferType(program: Program): InferredTypes.InferredType {
@@ -235,15 +282,24 @@ class TypecastExpression(var expression: Expression, var type: DataType, val imp
        expression.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression && node===expression)
+        expression = replacement
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun referencesIdentifiers(vararg name: String) = expression.referencesIdentifiers(*name)
    override fun inferType(program: Program): InferredTypes.InferredType = InferredTypes.knownFor(type)
    override fun constValue(program: Program): NumericLiteralValue? {
        val cv = expression.constValue(program) ?: return null
-        return cv.cast(type)
-        // val value = RuntimeValue(cv.type, cv.asNumericValue!!).cast(type)
-        // return LiteralValue.fromNumber(value.numericValue(), value.type, position).cast(type)
+        val cast = cv.cast(type)
+        return if(cast.isValid)
+            cast.valueOrZero()
+        else
+            null
    }

    override fun toString(): String {
@@ -259,11 +315,17 @@ data class AddressOf(var identifier: IdentifierReference, override val position:
        identifier.parent=this
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is IdentifierReference && node===identifier)
+        identifier = replacement
+        replacement.parent = this
+    }
+
    override fun constValue(program: Program): NumericLiteralValue? = null
    override fun referencesIdentifiers(vararg name: String) = false
    override fun inferType(program: Program): InferredTypes.InferredType = InferredTypes.knownFor(DataType.UWORD)
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
 }

 class DirectMemoryRead(var addressExpression: Expression, override val position: Position) : Expression(), IAssignable {
@@ -274,8 +336,15 @@ class DirectMemoryRead(var addressExpression: Expression, override val position:
        this.addressExpression.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression && node===addressExpression)
+        addressExpression = replacement
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun referencesIdentifiers(vararg name: String) = false
    override fun inferType(program: Program): InferredTypes.InferredType = InferredTypes.knownFor(DataType.UBYTE)
    override fun constValue(program: Program): NumericLiteralValue? = null
@@ -325,11 +394,15 @@ class NumericLiteralValue(val type: DataType,    // only numerical types allowed
        this.parent = parent
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        throw FatalAstException("can't replace here")
+    }
+
    override fun referencesIdentifiers(vararg name: String) = false
    override fun constValue(program: Program) = this

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)

    override fun toString(): String = "NumericLiteral(${type.name}:$number)"

@@ -345,82 +418,66 @@ class NumericLiteralValue(val type: DataType,    // only numerical types allowed

    operator fun compareTo(other: NumericLiteralValue): Int = number.toDouble().compareTo(other.number.toDouble())

-    fun cast(targettype: DataType): NumericLiteralValue {
+    class CastValue(val isValid: Boolean, private val value: NumericLiteralValue?) {
+        fun valueOrZero() = if(isValid) value!! else NumericLiteralValue(DataType.UBYTE, 0, Position.DUMMY)
+    }
+
+    fun cast(targettype: DataType): CastValue {
        if(type==targettype)
-            return this
+            return CastValue(true, this)
        val numval = number.toDouble()
        when(type) {
            DataType.UBYTE -> {
                if(targettype== DataType.BYTE && numval <= 127)
-                    return NumericLiteralValue(targettype, number.toShort(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toShort(), position))
                if(targettype== DataType.WORD || targettype== DataType.UWORD)
-                    return NumericLiteralValue(targettype, number.toInt(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toInt(), position))
                if(targettype== DataType.FLOAT)
-                    return NumericLiteralValue(targettype, number.toDouble(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toDouble(), position))
            }
            DataType.BYTE -> {
                if(targettype== DataType.UBYTE && numval >= 0)
-                    return NumericLiteralValue(targettype, number.toShort(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toShort(), position))
                if(targettype== DataType.UWORD && numval >= 0)
-                    return NumericLiteralValue(targettype, number.toInt(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toInt(), position))
                if(targettype== DataType.WORD)
-                    return NumericLiteralValue(targettype, number.toInt(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toInt(), position))
                if(targettype== DataType.FLOAT)
-                    return NumericLiteralValue(targettype, number.toDouble(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toDouble(), position))
            }
            DataType.UWORD -> {
                if(targettype== DataType.BYTE && numval <= 127)
-                    return NumericLiteralValue(targettype, number.toShort(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toShort(), position))
                if(targettype== DataType.UBYTE && numval <= 255)
-                    return NumericLiteralValue(targettype, number.toShort(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toShort(), position))
                if(targettype== DataType.WORD && numval <= 32767)
-                    return NumericLiteralValue(targettype, number.toInt(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toInt(), position))
                if(targettype== DataType.FLOAT)
-                    return NumericLiteralValue(targettype, number.toDouble(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toDouble(), position))
            }
            DataType.WORD -> {
                if(targettype== DataType.BYTE && numval >= -128 && numval <=127)
-                    return NumericLiteralValue(targettype, number.toShort(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toShort(), position))
                if(targettype== DataType.UBYTE && numval >= 0 && numval <= 255)
-                    return NumericLiteralValue(targettype, number.toShort(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toShort(), position))
                if(targettype== DataType.UWORD && numval >=0)
-                    return NumericLiteralValue(targettype, number.toInt(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toInt(), position))
                if(targettype== DataType.FLOAT)
-                    return NumericLiteralValue(targettype, number.toDouble(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toDouble(), position))
            }
            DataType.FLOAT -> {
                if (targettype == DataType.BYTE && numval >= -128 && numval <=127)
-                    return NumericLiteralValue(targettype, number.toShort(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toShort(), position))
                if (targettype == DataType.UBYTE && numval >=0 && numval <= 255)
-                    return NumericLiteralValue(targettype, number.toShort(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toShort(), position))
                if (targettype == DataType.WORD && numval >= -32768 && numval <= 32767)
-                    return NumericLiteralValue(targettype, number.toInt(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toInt(), position))
                if (targettype == DataType.UWORD && numval >=0 && numval <= 65535)
-                    return NumericLiteralValue(targettype, number.toInt(), position)
+                    return CastValue(true, NumericLiteralValue(targettype, number.toInt(), position))
            }
            else -> {}
        }
-        throw ExpressionError("can't cast $type into $targettype", position)
-    }
-}
-
-class StructLiteralValue(var values: List<Expression>,
-                         override val position: Position): Expression() {
-    override lateinit var parent: Node
-
-    override fun linkParents(parent: Node) {
-        this.parent=parent
-        values.forEach { it.linkParents(this) }
-    }
-
-    override fun constValue(program: Program): NumericLiteralValue?  = null
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
-    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
-    override fun referencesIdentifiers(vararg name: String) = values.any { it.referencesIdentifiers(*name) }
-    override fun inferType(program: Program): InferredTypes.InferredType = InferredTypes.knownFor(DataType.STRUCT)
-
-    override fun toString(): String {
-        return "struct{ ${values.joinToString(", ")} }"
+        return CastValue(false, null)
    }
 }

@@ -436,10 +493,16 @@ class StringLiteralValue(val value: String,
    override fun linkParents(parent: Node) {
        this.parent = parent
    }
+
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        throw FatalAstException("can't replace here")
+    }
+
    override fun referencesIdentifiers(vararg name: String) = false
    override fun constValue(program: Program): NumericLiteralValue? = null
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun toString(): String = "'${escape(value)}'"
    override fun inferType(program: Program): InferredTypes.InferredType = InferredTypes.knownFor(DataType.STR)
    operator fun compareTo(other: StringLiteralValue): Int = value.compareTo(other.value)
@@ -462,12 +525,21 @@ class ArrayLiteralValue(val type: InferredTypes.InferredType,     // inferred be
        this.parent = parent
        value.forEach {it.linkParents(this)}
    }
+
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression)
+        val idx = value.indexOfFirst { it===node }
+        value[idx] = replacement
+        replacement.parent = this
+    }
+
    override fun referencesIdentifiers(vararg name: String) = value.any { it.referencesIdentifiers(*name) }
    override fun constValue(program: Program): NumericLiteralValue? = null
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun toString(): String = "$value"
-    override fun inferType(program: Program): InferredTypes.InferredType = if(type.isUnknown) type else guessDatatype(program)
+    override fun inferType(program: Program): InferredTypes.InferredType = if(type.isKnown) type else guessDatatype(program)

    operator fun compareTo(other: ArrayLiteralValue): Int = throw ExpressionError("cannot order compare arrays", position)
    override fun hashCode(): Int = Objects.hash(value, type)
@@ -515,14 +587,14 @@ class ArrayLiteralValue(val type: InferredTypes.InferredType,     // inferred be
                if(num==null) {
                    // an array of UWORDs could possibly also contain AddressOfs, other stuff can't be casted
                    if (elementType != DataType.UWORD || it !is AddressOf)
-                        return null
+                        return null  // can't cast a value of  the array, abort
                    it
                } else {
-                    try {
-                        num.cast(elementType)
-                    } catch(x: ExpressionError) {
-                        return null
-                    }
+                    val cast = num.cast(elementType)
+                    if(cast.isValid)
+                        cast.valueOrZero()
+                    else
+                        return null // can't cast a value of the array, abort
                }
            }.toTypedArray()
            return ArrayLiteralValue(InferredTypes.InferredType.known(targettype), castArray, position = position)
@@ -544,9 +616,21 @@ class RangeExpr(var from: Expression,
        step.linkParents(this)
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression)
+        when {
+            from===node -> from=replacement
+            to===node -> to=replacement
+            step===node -> step=replacement
+            else -> throw FatalAstException("invalid replacement")
+        }
+        replacement.parent = this
+    }
+
    override fun constValue(program: Program): NumericLiteralValue? = null
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun referencesIdentifiers(vararg name: String): Boolean  = from.referencesIdentifiers(*name) || to.referencesIdentifiers(*name)
    override fun inferType(program: Program): InferredTypes.InferredType {
        val fromDt=from.inferType(program)
@@ -558,7 +642,14 @@ class RangeExpr(var from: Expression,
            fromDt istype DataType.STR && toDt istype DataType.STR -> InferredTypes.knownFor(DataType.STR)
            fromDt istype DataType.WORD || toDt istype DataType.WORD -> InferredTypes.knownFor(DataType.ARRAY_W)
            fromDt istype DataType.BYTE || toDt istype DataType.BYTE -> InferredTypes.knownFor(DataType.ARRAY_B)
-            else -> InferredTypes.knownFor(DataType.ARRAY_UB)
+            else -> {
+                val fdt = fromDt.typeOrElse(DataType.STRUCT)
+                val tdt = toDt.typeOrElse(DataType.STRUCT)
+                if(fdt largerThan tdt)
+                    InferredTypes.knownFor(ElementArrayTypes.getValue(fdt))
+                else
+                    InferredTypes.knownFor(ElementArrayTypes.getValue(tdt))
+            }
        }
    }
    override fun toString(): String {
@@ -580,8 +671,8 @@ class RangeExpr(var from: Expression,
        val toString = to as? StringLiteralValue
        if(fromString!=null && toString!=null ) {
            // string range -> int range over character values
-            fromVal = CompilationTarget.encodeString(fromString.value, fromString.altEncoding)[0].toInt()
-            toVal = CompilationTarget.encodeString(toString.value, fromString.altEncoding)[0].toInt()
+            fromVal = CompilationTarget.instance.encodeString(fromString.value, fromString.altEncoding)[0].toInt()
+            toVal = CompilationTarget.instance.encodeString(toString.value, fromString.altEncoding)[0].toInt()
        } else {
            val fromLv = from as? NumericLiteralValue
            val toLv = to as? NumericLiteralValue
@@ -611,24 +702,6 @@ internal fun makeRange(fromVal: Int, toVal: Int, stepVal: Int): IntProgression {
    }
 }

-class RegisterExpr(val register: Register, override val position: Position) : Expression(), IAssignable {
-    override lateinit var parent: Node
-
-    override fun linkParents(parent: Node) {
-        this.parent = parent
-    }
-
-    override fun constValue(program: Program): NumericLiteralValue? = null
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
-    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
-    override fun referencesIdentifiers(vararg name: String): Boolean = register.name in name
-    override fun toString(): String {
-        return "RegisterExpr(register=$register, pos=$position)"
-    }
-
-    override fun inferType(program: Program): InferredTypes.InferredType = InferredTypes.knownFor(DataType.UBYTE)
-}
-
 data class IdentifierReference(val nameInSource: List<String>, override val position: Position) : Expression(), IAssignable {
    override lateinit var parent: Node

@@ -641,10 +714,17 @@ data class IdentifierReference(val nameInSource: List<String>, override val posi
    fun targetVarDecl(namespace: INameScope): VarDecl? = targetStatement(namespace) as? VarDecl
    fun targetSubroutine(namespace: INameScope): Subroutine? = targetStatement(namespace) as? Subroutine

+    override fun equals(other: Any?) = other is IdentifierReference && other.nameInSource==nameInSource
+    override fun hashCode() = nameInSource.hashCode()
+
    override fun linkParents(parent: Node) {
        this.parent = parent
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        throw FatalAstException("can't replace here")
+    }
+
    override fun constValue(program: Program): NumericLiteralValue? {
        val node = program.namespace.lookup(nameInSource, this)
                ?: throw UndefinedSymbolError(this)
@@ -661,16 +741,17 @@ data class IdentifierReference(val nameInSource: List<String>, override val posi
        return "IdentifierRef($nameInSource)"
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
-    override fun referencesIdentifiers(vararg name: String): Boolean = nameInSource.last() in name
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
+    override fun referencesIdentifiers(vararg name: String): Boolean =
+            nameInSource.size==name.size && nameInSource.toTypedArray().contentEquals(name)

    override fun inferType(program: Program): InferredTypes.InferredType {
-        val targetStmt = targetStatement(program.namespace)
-        if(targetStmt is VarDecl) {
-            return InferredTypes.knownFor(targetStmt.datatype)
-        } else {
-            throw FatalAstException("cannot get datatype from identifier reference ${this}, pos=$position")
+        return when (val targetStmt = targetStatement(program.namespace)) {
+            is VarDecl -> InferredTypes.knownFor(targetStmt.datatype)
+            is StructDecl -> InferredTypes.knownFor(DataType.STRUCT)
+            else -> InferredTypes.InferredType.unknown()
        }
    }

@@ -699,6 +780,16 @@ class FunctionCall(override var target: IdentifierReference,
        args.forEach { it.linkParents(this) }
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        if(node===target)
+            target=replacement as IdentifierReference
+        else {
+            val idx = args.indexOfFirst { it===node }
+            args[idx] = replacement as Expression
+        }
+        replacement.parent = this
+    }
+
    override fun constValue(program: Program) = constValue(program, true)

    private fun constValue(program: Program, withDatatypeCheck: Boolean): NumericLiteralValue? {
@@ -729,14 +820,19 @@ class FunctionCall(override var target: IdentifierReference,
            // const-evaluating the builtin function call failed.
            return null
        }
+        catch(x: CannotEvaluateException) {
+            // const-evaluating the builtin function call failed.
+            return null
+        }
    }

    override fun toString(): String {
        return "FunctionCall(target=$target, pos=$position)"
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node)= visitor.visit(this, parent)
+
    override fun referencesIdentifiers(vararg name: String): Boolean = target.referencesIdentifiers(*name) || args.any{it.referencesIdentifiers(*name)}

    override fun inferType(program: Program): InferredTypes.InferredType {
@@ -1,41 +0,0 @@
-package prog8.ast.processing
-
-import prog8.ast.Program
-import prog8.ast.base.ErrorReporter
-import prog8.ast.statements.AnonymousScope
-import prog8.ast.statements.Statement
-import prog8.ast.statements.VarDecl
-
-class AnonymousScopeVarsCleanup(private val errors: ErrorReporter): IAstModifyingVisitor {
-    private val varsToMove: MutableMap<AnonymousScope, List<VarDecl>> = mutableMapOf()
-
-    override fun visit(program: Program) {
-        varsToMove.clear()
-        super.visit(program)
-        for((scope, decls) in varsToMove) {
-            val sub = scope.definingSubroutine()!!
-            val existingVariables = sub.statements.filterIsInstance<VarDecl>().associateBy { it.name }
-            var conflicts = false
-            decls.forEach {
-                val existing = existingVariables[it.name]
-                if (existing!=null) {
-                    errors.err("variable ${it.name} already defined in subroutine ${sub.name} at ${existing.position}", it.position)
-                    conflicts = true
-                }
-            }
-            if (!conflicts) {
-                decls.forEach { scope.remove(it) }
-                sub.statements.addAll(0, decls)
-                decls.forEach { it.parent = sub }
-            }
-        }
-    }
-
-    override fun visit(scope: AnonymousScope): Statement {
-        val scope2 = super.visit(scope) as AnonymousScope
-        val vardecls = scope2.statements.filterIsInstance<VarDecl>()
-        varsToMove[scope2] = vardecls
-        return scope2
-    }
-}
-
@@ -7,7 +7,9 @@ import prog8.ast.base.*
 import prog8.ast.expressions.*
 import prog8.ast.statements.*
 import prog8.compiler.CompilationOptions
+import prog8.compiler.target.C64Target
 import prog8.compiler.target.CompilationTarget
+import prog8.compiler.target.Cx16Target
 import prog8.functions.BuiltinFunctions
 import java.io.File

@@ -21,9 +23,11 @@ internal class AstChecker(private val program: Program,
        val mainBlocks = program.modules.flatMap { it.statements }.filter { b -> b is Block && b.name=="main" }.map { it as Block }
        if(mainBlocks.size>1)
            errors.err("more than one 'main' block", mainBlocks[0].position)
+        if(mainBlocks.isEmpty())
+            errors.err("there is no 'main' block", program.modules.firstOrNull()?.position ?: program.position)

        for(mainBlock in mainBlocks) {
-            val startSub = mainBlock.subScopes()["start"] as? Subroutine
+            val startSub = mainBlock.subScope("start") as? Subroutine
            if (startSub == null) {
                errors.err("missing program entrypoint ('start' subroutine in 'main' block)", mainBlock.position)
            } else {
@@ -40,7 +44,6 @@ internal class AstChecker(private val program: Program,
                    is VarDecl -> true
                    is InlineAssembly -> true
                    is INameScope -> true
-                    is VariableInitializationAssignment -> true
                    is NopStatement -> true
                    else -> false
                }
@@ -57,7 +60,7 @@ internal class AstChecker(private val program: Program,
        if(irqBlocks.size>1)
            errors.err("more than one 'irq' block", irqBlocks[0].position)
        for(irqBlock in irqBlocks) {
-            val irqSub = irqBlock.subScopes()["irq"] as? Subroutine
+            val irqSub = irqBlock.subScope("irq") as? Subroutine
            if (irqSub != null) {
                if (irqSub.parameters.isNotEmpty() || irqSub.returntypes.isNotEmpty())
                    errors.err("irq entrypoint subroutine can't have parameters and/or return values", irqSub.position)
@@ -81,7 +84,7 @@ internal class AstChecker(private val program: Program,
    override fun visit(returnStmt: Return) {
        val expectedReturnValues = returnStmt.definingSubroutine()?.returntypes ?: emptyList()
        if(expectedReturnValues.size>1) {
-            throw AstException("cannot use a return with one value in a subroutine that has multiple return values: $returnStmt")
+            throw FatalAstException("cannot use a return with one value in a subroutine that has multiple return values: $returnStmt")
        }

        if(expectedReturnValues.isEmpty() && returnStmt.value!=null) {
@@ -96,7 +99,7 @@ internal class AstChecker(private val program: Program,
                errors.err("return value type mismatch", returnStmt.value!!.position)
            } else {
                if (expectedReturnValues[0] != valueDt.typeOrElse(DataType.STRUCT))
-                    errors.err("type $valueDt of return value doesn't match subroutine's return type", returnStmt.value!!.position)
+                    errors.err("type $valueDt of return value doesn't match subroutine's return type ${expectedReturnValues[0]}", returnStmt.value!!.position)
            }
        }
        super.visit(returnStmt)
@@ -109,48 +112,57 @@ internal class AstChecker(private val program: Program,
    }

    override fun visit(forLoop: ForLoop) {
-        if(forLoop.body.containsNoCodeNorVars())
-            errors.warn("for loop body is empty", forLoop.position)
-
        val iterableDt = forLoop.iterable.inferType(program).typeOrElse(DataType.BYTE)
        if(iterableDt !in IterableDatatypes && forLoop.iterable !is RangeExpr) {
            errors.err("can only loop over an iterable type", forLoop.position)
        } else {
-            if (forLoop.loopRegister != null) {
-                // loop register
-                if (iterableDt != DataType.ARRAY_UB && iterableDt != DataType.ARRAY_B && iterableDt != DataType.STR)
-                    errors.err("register can only loop over bytes", forLoop.position)
-                if(forLoop.loopRegister!=Register.A)
-                    errors.err("it's only possible to use A as a loop register", forLoop.position)
+            val loopvar = forLoop.loopVar.targetVarDecl(program.namespace)
+            if(loopvar==null || loopvar.type== VarDeclType.CONST) {
+                errors.err("for loop requires a variable to loop with", forLoop.position)
            } else {
-                // loop variable
-                val loopvar = forLoop.loopVar!!.targetVarDecl(program.namespace)
-                if(loopvar==null || loopvar.type== VarDeclType.CONST) {
-                    errors.err("for loop requires a variable to loop with", forLoop.position)
-                } else {
-                    when (loopvar.datatype) {
-                        DataType.UBYTE -> {
-                            if(iterableDt!= DataType.UBYTE && iterableDt!= DataType.ARRAY_UB && iterableDt != DataType.STR)
-                                errors.err("ubyte loop variable can only loop over unsigned bytes or strings", forLoop.position)
-                        }
-                        DataType.UWORD -> {
-                            if(iterableDt!= DataType.UBYTE && iterableDt!= DataType.UWORD && iterableDt != DataType.STR &&
-                                    iterableDt != DataType.ARRAY_UB && iterableDt!= DataType.ARRAY_UW)
-                                errors.err("uword loop variable can only loop over unsigned bytes, words or strings", forLoop.position)
-                        }
-                        DataType.BYTE -> {
-                            if(iterableDt!= DataType.BYTE && iterableDt!= DataType.ARRAY_B)
-                                errors.err("byte loop variable can only loop over bytes", forLoop.position)
-                        }
-                        DataType.WORD -> {
-                            if(iterableDt!= DataType.BYTE && iterableDt!= DataType.WORD &&
-                                    iterableDt != DataType.ARRAY_B && iterableDt!= DataType.ARRAY_W)
-                                errors.err("word loop variable can only loop over bytes or words", forLoop.position)
-                        }
-                        DataType.FLOAT -> {
-                            errors.err("for loop only supports integers", forLoop.position)
-                        }
-                        else -> errors.err("loop variable must be numeric type", forLoop.position)
+
+                fun checkLoopRangeValues() {
+
+                }
+
+                when (loopvar.datatype) {
+                    DataType.UBYTE -> {
+                        if(iterableDt!= DataType.UBYTE && iterableDt!= DataType.ARRAY_UB && iterableDt != DataType.STR)
+                            errors.err("ubyte loop variable can only loop over unsigned bytes or strings", forLoop.position)
+                    }
+                    DataType.UWORD -> {
+                        if(iterableDt!= DataType.UBYTE && iterableDt!= DataType.UWORD && iterableDt != DataType.STR &&
+                                iterableDt != DataType.ARRAY_UB && iterableDt!= DataType.ARRAY_UW)
+                            errors.err("uword loop variable can only loop over unsigned bytes, words or strings", forLoop.position)
+                    }
+                    DataType.BYTE -> {
+                        if(iterableDt!= DataType.BYTE && iterableDt!= DataType.ARRAY_B)
+                            errors.err("byte loop variable can only loop over bytes", forLoop.position)
+                    }
+                    DataType.WORD -> {
+                        if(iterableDt!= DataType.BYTE && iterableDt!= DataType.WORD &&
+                                iterableDt != DataType.ARRAY_B && iterableDt!= DataType.ARRAY_W)
+                            errors.err("word loop variable can only loop over bytes or words", forLoop.position)
+                    }
+                    DataType.FLOAT -> {
+                        errors.err("for loop only supports integers", forLoop.position)
+                    }
+                    else -> errors.err("loop variable must be numeric type", forLoop.position)
+                }
+                if(errors.isEmpty()) {
+                    // check loop range values
+                    val range = forLoop.iterable as? RangeExpr
+                    if(range!=null) {
+                        val from = range.from as? NumericLiteralValue
+                        val to = range.to as? NumericLiteralValue
+                        if(from != null)
+                            checkValueTypeAndRange(loopvar.datatype, from)
+                        else if(!range.from.inferType(program).istype(loopvar.datatype))
+                            errors.err("range start value is incompatible with loop variable type", range.position)
+                        if(to != null)
+                            checkValueTypeAndRange(loopvar.datatype, to)
+                        else if(!range.to.inferType(program).istype(loopvar.datatype))
+                            errors.err("range end value is incompatible with loop variable type", range.position)
                    }
                }
            }
@@ -259,27 +271,27 @@ internal class AstChecker(private val program: Program,
                }
            }

-            val regCounts = mutableMapOf<Register, Int>().withDefault { 0 }
+            val regCounts = mutableMapOf<CpuRegister, Int>().withDefault { 0 }
            val statusflagCounts = mutableMapOf<Statusflag, Int>().withDefault { 0 }
            fun countRegisters(from: Iterable<RegisterOrStatusflag>) {
                regCounts.clear()
                statusflagCounts.clear()
                for(p in from) {
                    when(p.registerOrPair) {
-                        RegisterOrPair.A -> regCounts[Register.A]=regCounts.getValue(Register.A)+1
-                        RegisterOrPair.X -> regCounts[Register.X]=regCounts.getValue(Register.X)+1
-                        RegisterOrPair.Y -> regCounts[Register.Y]=regCounts.getValue(Register.Y)+1
+                        RegisterOrPair.A -> regCounts[CpuRegister.A]=regCounts.getValue(CpuRegister.A)+1
+                        RegisterOrPair.X -> regCounts[CpuRegister.X]=regCounts.getValue(CpuRegister.X)+1
+                        RegisterOrPair.Y -> regCounts[CpuRegister.Y]=regCounts.getValue(CpuRegister.Y)+1
                        RegisterOrPair.AX -> {
-                            regCounts[Register.A]=regCounts.getValue(Register.A)+1
-                            regCounts[Register.X]=regCounts.getValue(Register.X)+1
+                            regCounts[CpuRegister.A]=regCounts.getValue(CpuRegister.A)+1
+                            regCounts[CpuRegister.X]=regCounts.getValue(CpuRegister.X)+1
                        }
                        RegisterOrPair.AY -> {
-                            regCounts[Register.A]=regCounts.getValue(Register.A)+1
-                            regCounts[Register.Y]=regCounts.getValue(Register.Y)+1
+                            regCounts[CpuRegister.A]=regCounts.getValue(CpuRegister.A)+1
+                            regCounts[CpuRegister.Y]=regCounts.getValue(CpuRegister.Y)+1
                        }
                        RegisterOrPair.XY -> {
-                            regCounts[Register.X]=regCounts.getValue(Register.X)+1
-                            regCounts[Register.Y]=regCounts.getValue(Register.Y)+1
+                            regCounts[CpuRegister.X]=regCounts.getValue(CpuRegister.X)+1
+                            regCounts[CpuRegister.Y]=regCounts.getValue(CpuRegister.Y)+1
                        }
                        null ->
                            if(p.statusflag!=null)
@@ -315,26 +327,19 @@ internal class AstChecker(private val program: Program,
        } else {
            // Pass-by-reference datatypes can not occur as parameters to a subroutine directly
            // Instead, their reference (address) should be passed (as an UWORD).
-            // The language has no typed pointers at this time.
            if(subroutine.parameters.any{it.type in PassByReferenceDatatypes }) {
-                err("Pass-by-reference types (str, array) cannot occur as a parameter type directly. Instead, use an uword for their address, or access the variable from the outer scope directly.")
+                err("Pass-by-reference types (str, array) cannot occur as a parameter type directly. Instead, use an uword to receive their address, or access the variable from the outer scope directly.")
            }
        }
-
-        visitStatements(subroutine.statements)
    }

-    override fun visit(repeatLoop: RepeatLoop) {
-        if(repeatLoop.untilCondition.referencesIdentifiers("A", "X", "Y"))
-            errors.warn("using a register in the loop condition is risky (it could get clobbered)", repeatLoop.untilCondition.position)
-        if(repeatLoop.untilCondition.inferType(program).typeOrElse(DataType.STRUCT) !in IntegerDatatypes)
-            errors.err("condition value should be an integer type", repeatLoop.untilCondition.position)
-        super.visit(repeatLoop)
+    override fun visit(untilLoop: UntilLoop) {
+        if(untilLoop.untilCondition.inferType(program).typeOrElse(DataType.STRUCT) !in IntegerDatatypes)
+            errors.err("condition value should be an integer type", untilLoop.untilCondition.position)
+        super.visit(untilLoop)
    }

    override fun visit(whileLoop: WhileLoop) {
-        if(whileLoop.condition.referencesIdentifiers("A", "X", "Y"))
-            errors.warn("using a register in the loop condition is risky (it could get clobbered)", whileLoop.condition.position)
        if(whileLoop.condition.inferType(program).typeOrElse(DataType.STRUCT) !in IntegerDatatypes)
            errors.err("condition value should be an integer type", whileLoop.condition.position)
        super.visit(whileLoop)
@@ -356,17 +361,40 @@ internal class AstChecker(private val program: Program,
            }
        }

-        val sourceIdent = assignment.value as? IdentifierReference
        val targetIdent = assignment.target.identifier
-        if(sourceIdent!=null && targetIdent!=null) {
-            val sourceVar = sourceIdent.targetVarDecl(program.namespace)
+        if(targetIdent!=null) {
            val targetVar = targetIdent.targetVarDecl(program.namespace)
-            if(sourceVar?.struct!=null && targetVar?.struct!=null) {
-                if(sourceVar.struct!==targetVar.struct)
-                    errors.err("assignment of different struct types", assignment.position)
+            if(targetVar?.struct != null) {
+                val sourceStructLv = assignment.value as? ArrayLiteralValue
+                if (sourceStructLv != null) {
+                    if (sourceStructLv.value.size != targetVar.struct?.numberOfElements)
+                        errors.err("number of elements doesn't match struct definition", sourceStructLv.position)
+                } else {
+                    val sourceIdent = assignment.value as? IdentifierReference
+                    if (sourceIdent != null) {
+                        val sourceVar = sourceIdent.targetVarDecl(program.namespace)
+                        if (sourceVar?.struct != null) {
+                            if (sourceVar.struct !== targetVar.struct)
+                                errors.err("assignment of different struct types", assignment.position)
+                        }
+                    }
+                }
            }
        }

+        val targetDt = assignment.target.inferType(program, assignment)
+        if(assignment.value.inferType(program) != targetDt) {
+            if(targetDt.typeOrElse(DataType.STRUCT) in IterableDatatypes)
+                errors.err("cannot assign value to string or array", assignment.value.position)
+            else
+                errors.err("value's type doesn't match target", assignment.value.position)
+        }
+
+        if(assignment.value is TypecastExpression) {
+            if(assignment.isAugmentable && targetDt.istype(DataType.FLOAT))
+                errors.err("typecasting a float value in-place makes no sense", assignment.value.position)
+        }
+
        super.visit(assignment)
    }

@@ -383,8 +411,7 @@ internal class AstChecker(private val program: Program,
        val targetIdentifier = assignTarget.identifier
        if (targetIdentifier != null) {
            val targetName = targetIdentifier.nameInSource
-            val targetSymbol = program.namespace.lookup(targetName, assignment)
-            when (targetSymbol) {
+            when (val targetSymbol = program.namespace.lookup(targetName, assignment)) {
                null -> {
                    errors.err("undefined symbol: ${targetIdentifier.nameInSource.joinToString(".")}", targetIdentifier.position)
                    return
@@ -401,15 +428,14 @@ internal class AstChecker(private val program: Program,
                }
            }
        }
-        val targetDt = assignTarget.inferType(program, assignment).typeOrElse(DataType.STR)
-        if(targetDt in IterableDatatypes)
-            errors.err("cannot assign to a string or array type", assignTarget.position)
+
+// target type check is already done at the Assignment:
+//        val targetDt = assignTarget.inferType(program, assignment).typeOrElse(DataType.STR)
+//        if(targetDt in IterableDatatypes)
+//            errors.err("cannot assign to a string or array type", assignTarget.position)

        if (assignment is Assignment) {

-            if (assignment.aug_op != null)
-                throw FatalAstException("augmented assignment should have been converted into normal assignment")
-
            val targetDatatype = assignTarget.inferType(program, assignment)
            if (targetDatatype.isKnown) {
                val constVal = assignment.value.constValue(program)
@@ -438,21 +464,20 @@ internal class AstChecker(private val program: Program,
        if(variable==null)
            errors.err("pointer-of operand must be the name of a heap variable", addressOf.position)
        else {
-            if(variable.datatype !in ArrayDatatypes && variable.datatype != DataType.STR && variable.datatype!=DataType.STRUCT)
+            if(variable.datatype !in ArrayDatatypes
+                    && variable.type!=VarDeclType.MEMORY
+                    && variable.datatype != DataType.STR && variable.datatype!=DataType.STRUCT)
                errors.err("invalid pointer-of operand type", addressOf.position)
        }
        super.visit(addressOf)
    }

    override fun visit(decl: VarDecl) {
-        fun err(msg: String, position: Position?=null) {
-            err(msg, position ?: decl.position)
-        }
+        fun err(msg: String, position: Position?=null) = errors.err(msg, position ?: decl.position)

        // the initializer value can't refer to the variable itself (recursive definition)
-        if(decl.value?.referencesIdentifiers(decl.name) == true || decl.arraysize?.index?.referencesIdentifiers(decl.name) == true) {
+        if(decl.value?.referencesIdentifiers(decl.name) == true || decl.arraysize?.index?.referencesIdentifiers(decl.name) == true)
            err("recursive var declaration")
-        }

        // CONST can only occur on simple types (byte, word, float)
        if(decl.type== VarDeclType.CONST) {
@@ -460,10 +485,12 @@ internal class AstChecker(private val program: Program,
                err("const modifier can only be used on numeric types (byte, word, float)")
        }

-        // FLOATS
-        if(!compilerOptions.floats && decl.datatype in setOf(DataType.FLOAT, DataType.ARRAY_F) && decl.type!= VarDeclType.MEMORY) {
+        // FLOATS enabled?
+        if(!compilerOptions.floats && decl.datatype in setOf(DataType.FLOAT, DataType.ARRAY_F) && decl.type!= VarDeclType.MEMORY)
            err("floating point used, but that is not enabled via options")
-        }
+
+        if(decl.datatype == DataType.FLOAT && (decl.zeropage==ZeropageWish.REQUIRE_ZEROPAGE || decl.zeropage==ZeropageWish.PREFER_ZEROPAGE))
+            errors.warn("floating point values won't be placed in Zeropage due to size constraints", decl.position)

        // ARRAY without size specifier MUST have an iterable initializer value
        if(decl.isArray && decl.arraysize==null) {
@@ -493,57 +520,24 @@ internal class AstChecker(private val program: Program,
                    if(decl.zeropage==ZeropageWish.PREFER_ZEROPAGE || decl.zeropage==ZeropageWish.REQUIRE_ZEROPAGE)
                        err("struct can not be in zeropage")
                }
-                if (decl.value == null) {
-                    when {
-                        decl.datatype in NumericDatatypes -> {
-                            // initialize numeric var with value zero by default.
-                            val litVal =
-                                    when (decl.datatype) {
-                                        in ByteDatatypes -> NumericLiteralValue(decl.datatype, 0, decl.position)
-                                        in WordDatatypes -> NumericLiteralValue(decl.datatype, 0, decl.position)
-                                        else -> NumericLiteralValue(decl.datatype, 0.0, decl.position)
-                                    }
-                            litVal.parent = decl
-                            decl.value = litVal
-                        }
-                        decl.datatype == DataType.STRUCT -> {
-                            // structs may be initialized with an array, but it's okay to not initialize them as well.
-                        }
-                        decl.type == VarDeclType.VAR -> {
-                            if(decl.datatype in ArrayDatatypes) {
-                                // array declaration can have an optional initialization value
-                                // if it is absent, the size must be given, which should have been checked earlier
-                                if(decl.value==null && decl.arraysize==null)
-                                    throw FatalAstException("array init check failed")
-                            }
-                        }
-                        else -> err("var/const declaration needs a compile-time constant initializer value for type ${decl.datatype}")
-                        // const fold should have provided it!
-                    }
-                    super.visit(decl)
-                    return
-                }
+
                when(decl.value) {
+                    null -> {
+                        // a vardecl without an initial value, don't bother with it
+                    }
                    is RangeExpr -> throw FatalAstException("range expression should have been converted to a true array value")
                    is StringLiteralValue -> {
                        checkValueTypeAndRangeString(decl.datatype, decl.value as StringLiteralValue)
                    }
                    is ArrayLiteralValue -> {
-                        val arraySpec = decl.arraysize ?: ArrayIndex.forArray(decl.value as ArrayLiteralValue)
-                        checkValueTypeAndRangeArray(decl.datatype, decl.struct, arraySpec, decl.value as ArrayLiteralValue)
-                    }
-                    is NumericLiteralValue -> {
-                        checkValueTypeAndRange(decl.datatype, decl.value as NumericLiteralValue)
-                    }
-                    is StructLiteralValue -> {
                        if(decl.datatype==DataType.STRUCT) {
                            val struct = decl.struct!!
-                            val structLv = decl.value as StructLiteralValue
-                            if(struct.numberOfElements != structLv.values.size) {
+                            val structLv = decl.value as ArrayLiteralValue
+                            if(struct.numberOfElements != structLv.value.size) {
                                errors.err("struct value has incorrect number of elements", structLv.position)
                                return
                            }
-                            for(value in structLv.values.zip(struct.statements)) {
+                            for(value in structLv.value.zip(struct.statements)) {
                                val memberdecl = value.second as VarDecl
                                val constValue = value.first.constValue(program)
                                if(constValue==null) {
@@ -556,18 +550,26 @@ internal class AstChecker(private val program: Program,
                                    return
                                }
                            }
+                        } else {
+                            val arraySpec = decl.arraysize ?: ArrayIndex.forArray(decl.value as ArrayLiteralValue)
+                            checkValueTypeAndRangeArray(decl.datatype, decl.struct, arraySpec, decl.value as ArrayLiteralValue)
                        }
                    }
+                    is NumericLiteralValue -> {
+                        checkValueTypeAndRange(decl.datatype, decl.value as NumericLiteralValue)
+                    }
                    else -> {
-                        err("var/const declaration needs a compile-time constant initializer value, or range, instead found: ${decl.value!!.javaClass.simpleName}")
-                        super.visit(decl)
-                        return
+                        if(decl.type==VarDeclType.CONST) {
+                            err("const declaration needs a compile-time constant initializer value, or range")
+                            super.visit(decl)
+                            return
+                        }
                    }
                }
            }
            VarDeclType.MEMORY -> {
                if(decl.arraysize!=null) {
-                    val arraySize = decl.arraysize!!.size() ?: 1
+                    val arraySize = decl.arraysize!!.constIndex() ?: 1
                    when(decl.datatype) {
                        DataType.ARRAY_B, DataType.ARRAY_UB ->
                            if(arraySize > 256)
@@ -582,17 +584,51 @@ internal class AstChecker(private val program: Program,
                    }
                }

-                if(decl.value !is NumericLiteralValue) {
-                    err("value of memory var decl is not a numeric literal (it is a ${decl.value!!.javaClass.simpleName}).", decl.value?.position)
-                } else {
+                if(decl.value is NumericLiteralValue) {
                    val value = decl.value as NumericLiteralValue
                    if (value.type !in IntegerDatatypes || value.number.toInt() < 0 || value.number.toInt() > 65535) {
                        err("memory address must be valid integer 0..\$ffff", decl.value?.position)
                    }
+                } else {
+                    err("value of memory mapped variable can only be a number, perhaps you meant to use an address pointer type instead?", decl.value?.position)
                }
            }
        }

+        val declValue = decl.value
+        if(declValue!=null && decl.type==VarDeclType.VAR) {
+            if(decl.datatype==DataType.STRUCT) {
+                val valueIdt = declValue.inferType(program)
+                if(valueIdt.isUnknown)
+                    throw AstException("invalid value type")
+                val valueDt = valueIdt.typeOrElse(DataType.STRUCT)
+                if(valueDt !in ArrayDatatypes)
+                    err("initialisation of struct should be with array value", declValue.position)
+            } else if (!declValue.inferType(program).istype(decl.datatype)) {
+                err("initialisation value has incompatible type (${declValue.inferType(program)}) for the variable (${decl.datatype})", declValue.position)
+            }
+        }
+
+        // array length limits
+        if(decl.isArray) {
+            val length = decl.arraysize!!.constIndex() ?: 1
+            when (decl.datatype) {
+                DataType.STR, DataType.ARRAY_UB, DataType.ARRAY_B -> {
+                    if(length==0 || length>256)
+                        err("string and byte array length must be 1-256")
+                }
+                DataType.ARRAY_UW, DataType.ARRAY_W -> {
+                    if(length==0 || length>128)
+                        err("word array length must be 1-128")
+                }
+                DataType.ARRAY_F -> {
+                    if(length==0 || length>51)
+                        err("float array length must be 1-51")
+                }
+                else -> {}
+            }
+        }
+
        super.visit(decl)
    }

@@ -676,6 +712,14 @@ internal class AstChecker(private val program: Program,
                else if(directive.args.map{it.name in setOf("enable_floats", "force_output")}.any { !it })
                    err("invalid option directive argument(s)")
            }
+            "%target" -> {
+                if(directive.parent !is Block && directive.parent !is Module)
+                    err("this directive may only occur in a block or at module level")
+                if(directive.args.size != 1)
+                    err("directive requires one argument")
+                if(directive.args.single().name !in setOf(C64Target.name, Cx16Target.name))
+                    err("invalid compilation target")
+            }
            else -> throw SyntaxError("invalid directive ${directive.directive}", directive.position)
        }
        super.visit(directive)
@@ -698,6 +742,11 @@ internal class AstChecker(private val program: Program,
            checkValueTypeAndRangeArray(array.type.typeOrElse(DataType.STRUCT), null, arrayspec, array)
        }

+        if(!array.value.all { it is NumericLiteralValue || it is AddressOf || it is StringLiteralValue }) {
+            // TODO for now, array literals have to consist of all compile time constant values...
+            errors.err("array literal doesn't consist of only compile time constant values", array.position)
+        }
+
        super.visit(array)
    }

@@ -707,21 +756,29 @@ internal class AstChecker(private val program: Program,
    }

    override fun visit(expr: PrefixExpression) {
+        val dt = expr.inferType(program).typeOrElse(DataType.STRUCT)
        if(expr.operator=="-") {
-            val dt = expr.inferType(program).typeOrElse(DataType.STRUCT)
            if (dt != DataType.BYTE && dt != DataType.WORD && dt != DataType.FLOAT) {
                errors.err("can only take negative of a signed number type", expr.position)
            }
        }
+        else if(expr.operator == "not") {
+            if(dt !in IntegerDatatypes)
+                errors.err("can only use boolean not on integer types", expr.position)
+        }
+        else if(expr.operator == "~") {
+            if(dt !in IntegerDatatypes)
+                errors.err("can only use bitwise invert on integer types", expr.position)
+        }
        super.visit(expr)
    }

    override fun visit(expr: BinaryExpression) {
        val leftIDt = expr.left.inferType(program)
        val rightIDt = expr.right.inferType(program)
-        if(!leftIDt.isKnown || !rightIDt.isKnown) {
-            throw FatalAstException("can't determine datatype of both expression operands $expr")
-        }
+        if(!leftIDt.isKnown || !rightIDt.isKnown)
+            return     // hopefully this error will be detected elsewhere
+
        val leftDt = leftIDt.typeOrElse(DataType.STRUCT)
        val rightDt = rightIDt.typeOrElse(DataType.STRUCT)

@@ -738,7 +795,7 @@ internal class AstChecker(private val program: Program,
            }
            "**" -> {
                if(leftDt in IntegerDatatypes)
-                    errors.err("power operator requires floating point", expr.position)
+                    errors.err("power operator requires floating point operands", expr.position)
            }
            "and", "or", "xor" -> {
                // only integer numeric operands accepted, and if literal constants, only boolean values accepted (0 or 1)
@@ -754,12 +811,6 @@ internal class AstChecker(private val program: Program,
                if(leftDt !in IntegerDatatypes || rightDt !in IntegerDatatypes)
                    errors.err("bitwise operator can only be used on integer operands", expr.right.position)
            }
-            "<<", ">>" -> {
-                // for now, bit-shifts can only shift by a constant number
-                val constRight = expr.right.constValue(program)
-                if(constRight==null)
-                    errors.err("bit-shift can only be done by a constant number (for now)", expr.right.position)
-            }
        }

        if(leftDt !in NumericDatatypes)
@@ -826,6 +877,10 @@ internal class AstChecker(private val program: Program,
                errors.warn("sgn() of unsigned type is always 0 or 1, this is perhaps not what was intended", functionCall.args.first().position)
        }

+        val error = VerifyFunctionArgTypes.checkTypes(functionCall, functionCall.definingScope(), program)
+        if(error!=null)
+            errors.err(error, functionCall.args.first().position)
+
        super.visit(functionCall)
    }

@@ -848,12 +903,18 @@ internal class AstChecker(private val program: Program,
            }
        }

-        if(functionCallStatement.target.nameInSource.last() in setOf("lsl", "lsr", "rol", "ror", "rol2", "ror2", "swap", "sort", "reverse")) {
+        if(functionCallStatement.target.nameInSource.last() in setOf("rol", "ror", "rol2", "ror2", "swap", "sort", "reverse")) {
            // in-place modification, can't be done on literals
-            if(functionCallStatement.args.any { it !is IdentifierReference && it !is RegisterExpr && it !is ArrayIndexedExpression && it !is DirectMemoryRead }) {
-                errors.err("can't use that as argument to a in-place modifying function", functionCallStatement.args.first().position)
+            if(functionCallStatement.args.any { it !is IdentifierReference && it !is ArrayIndexedExpression && it !is DirectMemoryRead }) {
+                errors.err("invalid argument to a in-place modifying function", functionCallStatement.args.first().position)
            }
        }
+
+        val error = VerifyFunctionArgTypes.checkTypes(functionCallStatement, functionCallStatement.definingScope(), program)
+        if(error!=null) {
+            errors.err(error, functionCallStatement.args.firstOrNull()?.position ?: functionCallStatement.position)
+        }
+
        super.visit(functionCallStatement)
    }

@@ -862,77 +923,35 @@ internal class AstChecker(private val program: Program,
            errors.err("cannot use arguments when calling a label", position)

        if(target is BuiltinFunctionStatementPlaceholder) {
-            // it's a call to a builtin function.
-            val func = BuiltinFunctions.getValue(target.name)
-            if(args.size!=func.parameters.size)
-                errors.err("invalid number of arguments", position)
-            else {
-                val paramTypesForAddressOf = PassByReferenceDatatypes + DataType.UWORD
-                for (arg in args.withIndex().zip(func.parameters)) {
-                    val argDt=arg.first.value.inferType(program)
-                    if (argDt.isKnown
-                            && !(argDt.typeOrElse(DataType.STRUCT) isAssignableTo arg.second.possibleDatatypes)
-                            && (argDt.typeOrElse(DataType.STRUCT) != DataType.UWORD || arg.second.possibleDatatypes.intersect(paramTypesForAddressOf).isEmpty())) {
-                        errors.err("builtin function '${target.name}' argument ${arg.first.index + 1} has invalid type $argDt, expected ${arg.second.possibleDatatypes}", position)
-                    }
+            if(target.name=="swap") {
+                // swap() is a bit weird because this one is translated into a operations directly, instead of being a function call
+                val dt1 = args[0].inferType(program)
+                val dt2 = args[1].inferType(program)
+                if (dt1 != dt2)
+                    errors.err("swap requires 2 args of identical type", position)
+                else if (args[0].constValue(program) != null || args[1].constValue(program) != null)
+                    errors.err("swap requires 2 variables, not constant value(s)", position)
+                else if(args[0] isSameAs args[1])
+                    errors.err("swap should have 2 different args", position)
+                else if(dt1.typeOrElse(DataType.STRUCT) !in NumericDatatypes)
+                    errors.err("swap requires args of numerical type", position)
+            }
+            else if(target.name=="all" || target.name=="any") {
+                if((args[0] as? AddressOf)?.identifier?.targetVarDecl(program.namespace)?.datatype == DataType.STR) {
+                    errors.err("any/all on a string is useless (is always true unless the string is empty)", position)
                }
-                if(target.name=="swap") {
-                    // swap() is a bit weird because this one is translated into a operations directly, instead of being a function call
-                    val dt1 = args[0].inferType(program)
-                    val dt2 = args[1].inferType(program)
-                    if (dt1 != dt2)
-                        errors.err("swap requires 2 args of identical type", position)
-                    else if (args[0].constValue(program) != null || args[1].constValue(program) != null)
-                        errors.err("swap requires 2 variables, not constant value(s)", position)
-                    else if(args[0] isSameAs args[1])
-                        errors.err("swap should have 2 different args", position)
-                    else if(dt1.typeOrElse(DataType.STRUCT) !in NumericDatatypes)
-                        errors.err("swap requires args of numerical type", position)
-                }
-                else if(target.name=="all" || target.name=="any") {
-                    if((args[0] as? AddressOf)?.identifier?.targetVarDecl(program.namespace)?.datatype == DataType.STR) {
-                        errors.err("any/all on a string is useless (is always true unless the string is empty)", position)
-                    }
-                    if(args[0].inferType(program).typeOrElse(DataType.STR) == DataType.STR) {
-                        errors.err("any/all on a string is useless (is always true unless the string is empty)", position)
-                    }
+                if(args[0].inferType(program).typeOrElse(DataType.STR) == DataType.STR) {
+                    errors.err("any/all on a string is useless (is always true unless the string is empty)", position)
                }
            }
        } else if(target is Subroutine) {
-            if(args.size!=target.parameters.size)
-                errors.err("invalid number of arguments", position)
-            else {
+            if(target.regXasResult())
+                errors.warn("subroutine call return value in X register is discarded and replaced by 0", position)
+            if(target.isAsmSubroutine) {
                for (arg in args.withIndex().zip(target.parameters)) {
                    val argIDt = arg.first.value.inferType(program)
-                    if(!argIDt.isKnown) {
+                    if (!argIDt.isKnown)
                        return
-                    }
-                    val argDt=argIDt.typeOrElse(DataType.STRUCT)
-                    if(!(argDt isAssignableTo arg.second.type)) {
-                        // for asm subroutines having STR param it's okay to provide a UWORD (address value)
-                        if(!(target.isAsmSubroutine && arg.second.type == DataType.STR && argDt == DataType.UWORD))
-                            errors.err("subroutine '${target.name}' argument ${arg.first.index + 1} has invalid type $argDt, expected ${arg.second.type}", position)
-                    }
-
-                    if(target.isAsmSubroutine) {
-                        if (target.asmParameterRegisters[arg.first.index].registerOrPair in setOf(RegisterOrPair.AX, RegisterOrPair.XY, RegisterOrPair.X)) {
-                            if (arg.first.value !is NumericLiteralValue && arg.first.value !is IdentifierReference)
-                                errors.warn("calling a subroutine that expects X as a parameter is problematic, more so when providing complex arguments. If you see a compiler error/crash about this later, try to simplify this call", position)
-                        }
-
-                        // check if the argument types match the register(pairs)
-                        val asmParamReg = target.asmParameterRegisters[arg.first.index]
-                        if(asmParamReg.statusflag!=null) {
-                            if(argDt !in ByteDatatypes)
-                                errors.err("subroutine '${target.name}' argument ${arg.first.index + 1} must be byte type for statusflag", position)
-                        } else if(asmParamReg.registerOrPair in setOf(RegisterOrPair.A, RegisterOrPair.X, RegisterOrPair.Y)) {
-                            if(argDt !in ByteDatatypes)
-                                errors.err("subroutine '${target.name}' argument ${arg.first.index + 1} must be byte type for single register", position)
-                        } else if(asmParamReg.registerOrPair in setOf(RegisterOrPair.AX, RegisterOrPair.AY, RegisterOrPair.XY)) {
-                            if(argDt !in WordDatatypes + IterableDatatypes)
-                                errors.err("subroutine '${target.name}' argument ${arg.first.index + 1} must be word type for register pair", position)
-                        }
-                    }
                }
            }
        }
@@ -972,7 +991,7 @@ internal class AstChecker(private val program: Program,
        if(target is VarDecl) {
            if(target.datatype !in IterableDatatypes)
                errors.err("indexing requires an iterable variable", arrayIndexedExpression.position)
-            val arraysize = target.arraysize?.size()
+            val arraysize = target.arraysize?.constIndex()
            if(arraysize!=null) {
                // check out of bounds
                val index = (arrayIndexedExpression.arrayspec.index as? NumericLiteralValue)?.number?.toInt()
@@ -1053,29 +1072,14 @@ internal class AstChecker(private val program: Program,
        }
    }

-    override fun visit(scope: AnonymousScope) {
-        visitStatements(scope.statements)
-    }
-
-    private fun visitStatements(statements: List<Statement>) {
-        for((index, stmt) in statements.withIndex()) {
-            if(stmt is FunctionCallStatement
-                    && stmt.target.nameInSource.last()=="exit"
-                    && index < statements.lastIndex)
-                errors.warn("unreachable code, exit call above never returns", statements[index+1].position)
-
-            if(stmt is Return && index < statements.lastIndex)
-                errors.warn("unreachable code, return statement above", statements[index+1].position)
-
-            stmt.accept(this)
-        }
-    }
-
    private fun checkFunctionOrLabelExists(target: IdentifierReference, statement: Statement): Statement? {
        val targetStatement = target.targetStatement(program.namespace)
        if(targetStatement is Label || targetStatement is Subroutine || targetStatement is BuiltinFunctionStatementPlaceholder)
            return targetStatement
-        errors.err("undefined function or subroutine: ${target.nameInSource.joinToString(".")}", statement.position)
+        else if(targetStatement==null)
+            errors.err("undefined function or subroutine: ${target.nameInSource.joinToString(".")}", statement.position)
+        else
+            errors.err("cannot call that: ${target.nameInSource.joinToString(".")}", statement.position)
        return null
    }

@@ -1099,7 +1103,7 @@ internal class AstChecker(private val program: Program,
        }

        if(value.type.isUnknown)
-            return err("attempt to check values of array with as yet unknown datatype")
+            return false

        when (targetDt) {
            DataType.STR -> return err("string value expected")
@@ -1108,7 +1112,7 @@ internal class AstChecker(private val program: Program,
                if(value.type.istype(targetDt)) {
                    if(!checkArrayValues(value, targetDt))
                        return false
-                    val arraySpecSize = arrayspec.size()
+                    val arraySpecSize = arrayspec.constIndex()
                    val arraySize = value.value.size
                    if(arraySpecSize!=null && arraySpecSize>0) {
                        if(arraySpecSize<1 || arraySpecSize>256)
@@ -1130,7 +1134,7 @@ internal class AstChecker(private val program: Program,
                if(value.type.istype(targetDt)) {
                    if(!checkArrayValues(value, targetDt))
                        return false
-                    val arraySpecSize = arrayspec.size()
+                    val arraySpecSize = arrayspec.constIndex()
                    val arraySize = value.value.size
                    if(arraySpecSize!=null && arraySpecSize>0) {
                        if(arraySpecSize<1 || arraySpecSize>128)
@@ -1153,7 +1157,7 @@ internal class AstChecker(private val program: Program,
                    if(!checkArrayValues(value, targetDt))
                        return false
                    val arraySize = value.value.size
-                    val arraySpecSize = arrayspec.size()
+                    val arraySpecSize = arrayspec.constIndex()
                    if(arraySpecSize!=null && arraySpecSize>0) {
                        if(arraySpecSize < 1 || arraySpecSize>51)
                            return err("float array length must be 1-51")
@@ -1168,7 +1172,7 @@ internal class AstChecker(private val program: Program,

                    // check if the floating point values are all within range
                    val doubles = value.value.map {it.constValue(program)?.number!!.toDouble()}.toDoubleArray()
-                    if(doubles.any { it < CompilationTarget.machine.FLOAT_MAX_NEGATIVE || it > CompilationTarget.machine.FLOAT_MAX_POSITIVE })
+                    if(doubles.any { it < CompilationTarget.instance.machine.FLOAT_MAX_NEGATIVE || it > CompilationTarget.instance.machine.FLOAT_MAX_POSITIVE })
                        return err("floating point value overflow")
                    return true
                }
@@ -1245,7 +1249,11 @@ internal class AstChecker(private val program: Program,
                is AddressOf -> it.identifier.heapId(program.namespace)
                is TypecastExpression -> {
                    val constVal = it.expression.constValue(program)
-                    constVal?.cast(it.type)?.number?.toInt() ?: -9999999
+                    val cast = constVal?.cast(it.type)
+                    if(cast==null || !cast.isValid)
+                        -9999999
+                    else
+                        cast.valueOrZero().number.toInt()
                }
                else -> -9999999
            }
@@ -1265,7 +1273,7 @@ internal class AstChecker(private val program: Program,
                correct = array.all { it in -32768..32767 }
            }
            DataType.ARRAY_F -> correct = true
-            else -> throw AstException("invalid array type $type")
+            else -> throw FatalAstException("invalid array type $type")
        }
        if (!correct)
            errors.err("array value out of range for type $type", value.position)
@@ -1290,8 +1298,8 @@ internal class AstChecker(private val program: Program,
            DataType.STR -> sourceDatatype== DataType.STR
            DataType.STRUCT -> {
                if(sourceDatatype==DataType.STRUCT) {
-                    val structLv = sourceValue as StructLiteralValue
-                    val numValues = structLv.values.size
+                    val structLv = sourceValue as ArrayLiteralValue
+                    val numValues = structLv.value.size
                    val targetstruct = target.identifier!!.targetVarDecl(program.namespace)!!.struct!!
                    return targetstruct.numberOfElements == numValues
                }
@@ -1,8 +1,6 @@
 package prog8.ast.processing

-import prog8.ast.INameScope
 import prog8.ast.Module
-import prog8.ast.Node
 import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.expressions.*
@@ -10,94 +8,83 @@ import prog8.ast.statements.*
 import prog8.compiler.target.CompilationTarget
 import prog8.functions.BuiltinFunctions

-
-internal class AstIdentifiersChecker(private val program: Program,
-                                     private val errors: ErrorReporter) : IAstModifyingVisitor {
+internal class AstIdentifiersChecker(private val program: Program, private val errors: ErrorReporter) : IAstVisitor {
    private var blocks = mutableMapOf<String, Block>()
-    private val vardeclsToAdd = mutableMapOf<INameScope, MutableList<VarDecl>>()

    private fun nameError(name: String, position: Position, existing: Statement) {
        errors.err("name conflict '$name', also defined in ${existing.position.file} line ${existing.position.line}", position)
    }

    override fun visit(module: Module) {
-        vardeclsToAdd.clear()
        blocks.clear()  // blocks may be redefined within a different module
+
        super.visit(module)
-        // add any new vardecls to the various scopes
-        for((where, decls) in vardeclsToAdd) {
-            where.statements.addAll(0, decls)
-            decls.forEach { it.linkParents(where as Node) }
-        }
    }

-    override fun visit(block: Block): Statement {
+    override fun visit(block: Block) {
+        if(block.name in CompilationTarget.instance.machine.opcodeNames)
+            errors.err("can't use a cpu opcode name as a symbol: '${block.name}'", block.position)
+
        val existing = blocks[block.name]
        if(existing!=null)
            nameError(block.name, block.position, existing)
        else
            blocks[block.name] = block

-        return super.visit(block)
+        super.visit(block)
    }

-    override fun visit(functionCall: FunctionCall): Expression {
-        if(functionCall.target.nameInSource.size==1 && functionCall.target.nameInSource[0]=="lsb") {
-            // lsb(...) is just an alias for type cast to ubyte, so replace with "... as ubyte"
-            val typecast = TypecastExpression(functionCall.args.single(), DataType.UBYTE, false, functionCall.position)
-            typecast.linkParents(functionCall.parent)
-            return super.visit(typecast)
+    override fun visit(directive: Directive) {
+        if(directive.directive=="%target") {
+            val compatibleTarget = directive.args.single().name
+            if (compatibleTarget != CompilationTarget.instance.name)
+                errors.err("module's compilation target ($compatibleTarget) differs from active target (${CompilationTarget.instance.name})", directive.position)
        }
-        return super.visit(functionCall)
+
+        super.visit(directive)
    }

-    override fun visit(decl: VarDecl): Statement {
-        // first, check if there are datatype errors on the vardecl
+    override fun visit(decl: VarDecl) {
        decl.datatypeErrors.forEach { errors.err(it.message, it.position) }

-        // now check the identifier
        if(decl.name in BuiltinFunctions)
-            // the builtin functions can't be redefined
            errors.err("builtin function cannot be redefined", decl.position)

-        if(decl.name in CompilationTarget.machine.opcodeNames)
+        if(decl.name in CompilationTarget.instance.machine.opcodeNames)
            errors.err("can't use a cpu opcode name as a symbol: '${decl.name}'", decl.position)

-        // is it a struct variable? then define all its struct members as mangled names,
-        //    and include the original decl as well.
        if(decl.datatype==DataType.STRUCT) {
-            if(decl.structHasBeenFlattened)
+            if (decl.structHasBeenFlattened)
                return super.visit(decl)    // don't do this multiple times

-            if(decl.struct==null) {
+            if (decl.struct == null) {
                errors.err("undefined struct type", decl.position)
                return super.visit(decl)
            }

-            if(decl.struct!!.statements.any { (it as VarDecl).datatype !in NumericDatatypes})
+            if (decl.struct!!.statements.any { (it as VarDecl).datatype !in NumericDatatypes })
                return super.visit(decl)     // a non-numeric member, not supported. proper error is given by AstChecker later

-            if(decl.value is NumericLiteralValue) {
+            if (decl.value is NumericLiteralValue) {
                errors.err("you cannot initialize a struct using a single value", decl.position)
                return super.visit(decl)
            }

-            val decls = decl.flattenStructMembers()
-            decls.add(decl)
-            val result = AnonymousScope(decls, decl.position)
-            result.linkParents(decl.parent)
-            return result
+            if (decl.value != null && decl.value !is ArrayLiteralValue) {
+                errors.err("initializing a struct requires array literal value", decl.value?.position ?: decl.position)
+                return super.visit(decl)
+            }
        }

        val existing = program.namespace.lookup(listOf(decl.name), decl)
        if (existing != null && existing !== decl)
            nameError(decl.name, decl.position, existing)

-        return super.visit(decl)
+        super.visit(decl)
    }

-    override fun visit(subroutine: Subroutine): Statement {
-        if(subroutine.name in CompilationTarget.machine.opcodeNames) {
+    override fun visit(subroutine: Subroutine) {
+        if(subroutine.name in CompilationTarget.instance.machine.opcodeNames) {
            errors.err("can't use a cpu opcode name as a symbol: '${subroutine.name}'", subroutine.position)
        } else if(subroutine.name in BuiltinFunctions) {
            // the builtin functions can't be redefined
@@ -111,14 +98,6 @@ internal class AstIdentifiersChecker(private val program: Program,
            if (existing != null && existing !== subroutine)
                nameError(subroutine.name, subroutine.position, existing)

-            // does the parameter redefine a variable declared elsewhere?
-            for(param in subroutine.parameters) {
-                val existingVar = subroutine.lookup(listOf(param.name), subroutine)
-                if (existingVar != null && existingVar.parent !== subroutine) {
-                    nameError(param.name, param.position, existingVar)
-                }
-            }
-
            // check that there are no local variables, labels, or other subs that redefine the subroutine's parameters
            val symbolsInSub = subroutine.allDefinedSymbols()
            val namesInSub = symbolsInSub.map{ it.first }.toSet()
@@ -133,32 +112,16 @@ internal class AstIdentifiersChecker(private val program: Program,
                    nameError(name, sub.position, subroutine)
            }

-            // inject subroutine params as local variables (if they're not there yet) (for non-kernel subroutines and non-asm parameters)
-            // NOTE:
-            // - numeric types BYTE and WORD and FLOAT are passed by value;
-            // - strings, arrays, matrices are passed by reference (their 16-bit address is passed as an uword parameter)
-            if(subroutine.asmAddress==null) {
-                if(subroutine.asmParameterRegisters.isEmpty()) {
-                    subroutine.parameters
-                            .filter { it.name !in namesInSub }
-                            .forEach {
-                                val vardecl = VarDecl(VarDeclType.VAR, it.type, ZeropageWish.NOT_IN_ZEROPAGE, null, it.name, null, null,
-                                        isArray = false, autogeneratedDontRemove = true, position = subroutine.position)
-                                vardecl.linkParents(subroutine)
-                                subroutine.statements.add(0, vardecl)
-                            }
-                }
-            }
-
            if(subroutine.isAsmSubroutine && subroutine.statements.any{it !is InlineAssembly}) {
                errors.err("asmsub can only contain inline assembly (%asm)", subroutine.position)
            }
        }
-        return super.visit(subroutine)
+
+        super.visit(subroutine)
    }

-    override fun visit(label: Label): Statement {
-        if(label.name in CompilationTarget.machine.opcodeNames)
+    override fun visit(label: Label) {
+        if(label.name in CompilationTarget.instance.machine.opcodeNames)
            errors.err("can't use a cpu opcode name as a symbol: '${label.name}'", label.position)

        if(label.name in BuiltinFunctions) {
@@ -175,176 +138,24 @@ internal class AstIdentifiersChecker(private val program: Program,
                }
            }
        }
-        return super.visit(label)
+
+        super.visit(label)
    }

-    override fun visit(forLoop: ForLoop): Statement {
-        // If the for loop has a decltype, it means to declare the loopvar inside the loop body
-        // rather than reusing an already declared loopvar from an outer scope.
-        // For loops that loop over an interable variable (instead of a range of numbers) get an
-        // additional interation count variable in their scope.
-        if(forLoop.loopRegister!=null) {
-            if(forLoop.loopRegister == Register.X)
-                errors.warn("writing to the X register is dangerous, because it's used as an internal pointer", forLoop.position)
-        } else {
-            val loopVar = forLoop.loopVar
-            if (loopVar != null) {
-                val validName = forLoop.body.name.replace("<", "").replace(">", "").replace("-", "")
-                val loopvarName = "prog8_loopvar_$validName"
-                if (forLoop.iterable !is RangeExpr) {
-                    val existing = if (forLoop.body.containsNoCodeNorVars()) null else forLoop.body.lookup(listOf(loopvarName), forLoop.body.statements.first())
-                    if (existing == null) {
-                        // create loop iteration counter variable (without value, to avoid an assignment)
-                        val vardecl = VarDecl(VarDeclType.VAR, DataType.UBYTE, ZeropageWish.PREFER_ZEROPAGE, null, loopvarName, null, null,
-                                isArray = false, autogeneratedDontRemove = true, position = loopVar.position)
-                        vardecl.linkParents(forLoop.body)
-                        forLoop.body.statements.add(0, vardecl)
-                        loopVar.parent = forLoop.body   // loopvar 'is defined in the body'
-                    }
-                }
-            }
-        }
-        return super.visit(forLoop)
+    override fun visit(string: StringLiteralValue) {
+        if (string.value.length !in 1..255)
+            errors.err("string literal length must be between 1 and 255", string.position)
+
+        super.visit(string)
    }

-    override fun visit(assignTarget: AssignTarget): AssignTarget {
-        if(assignTarget.register== Register.X)
-            errors.warn("writing to the X register is dangerous, because it's used as an internal pointer", assignTarget.position)
-        return super.visit(assignTarget)
-    }
-
-    override fun visit(returnStmt: Return): Statement {
-        if(returnStmt.value!=null) {
-            // possibly adjust any literal values returned, into the desired returning data type
-            val subroutine = returnStmt.definingSubroutine()!!
-            if(subroutine.returntypes.size!=1)
-                return returnStmt  // mismatch in number of return values, error will be printed later.
-            val lval = returnStmt.value as? NumericLiteralValue
-            returnStmt.value = lval?.cast(subroutine.returntypes.single()) ?: returnStmt.value!!
-        }
-        return super.visit(returnStmt)
-    }
-
-
-    override fun visit(arrayLiteral: ArrayLiteralValue): Expression {
-        val array = super.visit(arrayLiteral)
-        if(array is ArrayLiteralValue) {
-            val vardecl = array.parent as? VarDecl
-            // adjust the datatype of the array (to an educated guess)
-            if(vardecl!=null) {
-                val arrayDt = array.type
-                if(!arrayDt.istype(vardecl.datatype)) {
-                    val cast = array.cast(vardecl.datatype)
-                    if (cast != null) {
-                        vardecl.value = cast
-                        cast.linkParents(vardecl)
-                        return cast
-                    }
-                }
-                return array
-            }
-            else {
-                val arrayDt = array.guessDatatype(program)
-                if(arrayDt.isKnown) {
-                    // this array literal is part of an expression, turn it into an identifier reference
-                    val litval2 = array.cast(arrayDt.typeOrElse(DataType.STRUCT))
-                    return if (litval2 != null) {
-                        litval2.parent = array.parent
-                        makeIdentifierFromRefLv(litval2)
-                    } else array
-                }
-            }
-        }
-        return array
-    }
-
-    override fun visit(stringLiteral: StringLiteralValue): Expression {
-        val string = super.visit(stringLiteral)
-        if(string is StringLiteralValue) {
-            val vardecl = string.parent as? VarDecl
-            // intern the string; move it into the heap
-            if (string.value.length !in 1..255)
-                errors.err("string literal length must be between 1 and 255", string.position)
-            return if (vardecl != null)
-                string
-            else
-                makeIdentifierFromRefLv(string)  // replace the literal string by a identifier reference.
-        }
-        return string
-    }
-
-    private fun makeIdentifierFromRefLv(array: ArrayLiteralValue): IdentifierReference {
-        // a referencetype literal value that's not declared as a variable
-        // we need to introduce an auto-generated variable for this to be able to refer to the value
-        // note: if the var references the same literal value, it is not yet de-duplicated here.
-        val scope = array.definingScope()
-        val variable = VarDecl.createAuto(array)
-        return replaceWithIdentifier(variable, scope, array.parent)
-    }
-
-    private fun makeIdentifierFromRefLv(string: StringLiteralValue): IdentifierReference {
-        // a referencetype literal value that's not declared as a variable
-        // we need to introduce an auto-generated variable for this to be able to refer to the value
-        // note: if the var references the same literal value, it is not yet de-duplicated here.
-        val scope = string.definingScope()
-        val variable = VarDecl.createAuto(string)
-        return replaceWithIdentifier(variable, scope, string.parent)
-    }
-
-    private fun replaceWithIdentifier(variable: VarDecl, scope: INameScope, parent: Node): IdentifierReference {
-        val variable1 = addVarDecl(scope, variable)
-        // replace the reference literal by a identifier reference
-        val identifier = IdentifierReference(listOf(variable1.name), variable1.position)
-        identifier.parent = parent
-        return identifier
-    }
-
-    override fun visit(structDecl: StructDecl): Statement {
+    override fun visit(structDecl: StructDecl) {
        for(member in structDecl.statements){
            val decl = member as? VarDecl
            if(decl!=null && decl.datatype !in NumericDatatypes)
                errors.err("structs can only contain numerical types", decl.position)
        }

-        return super.visit(structDecl)
+        super.visit(structDecl)
    }
-
-    override fun visit(expr: BinaryExpression): Expression {
-        return when {
-            expr.left is StringLiteralValue ->
-                processBinaryExprWithString(expr.left as StringLiteralValue, expr.right, expr)
-            expr.right is StringLiteralValue ->
-                processBinaryExprWithString(expr.right as StringLiteralValue, expr.left, expr)
-            else -> super.visit(expr)
-        }
-    }
-
-    private fun processBinaryExprWithString(string: StringLiteralValue, operand: Expression, expr: BinaryExpression): Expression {
-        val constvalue = operand.constValue(program)
-        if(constvalue!=null) {
-            if (expr.operator == "*") {
-                // repeat a string a number of times
-                return StringLiteralValue(string.value.repeat(constvalue.number.toInt()), string.altEncoding, expr.position)
-            }
-        }
-        if(expr.operator == "+" && operand is StringLiteralValue) {
-            // concatenate two strings
-            return StringLiteralValue("${string.value}${operand.value}", string.altEncoding, expr.position)
-        }
-        return expr
-    }
-
-    private fun addVarDecl(scope: INameScope, variable: VarDecl): VarDecl {
-        if(scope !in vardeclsToAdd)
-            vardeclsToAdd[scope] = mutableListOf()
-        val declList = vardeclsToAdd.getValue(scope)
-        val existing = declList.singleOrNull { it.name==variable.name }
-        return if(existing!=null) {
-            existing
-        } else {
-            declList.add(variable)
-            variable
-        }
-    }
-
 }
@@ -2,6 +2,7 @@ package prog8.ast.processing

 import prog8.ast.INameScope
 import prog8.ast.base.ErrorReporter
+import prog8.ast.base.Position
 import prog8.ast.expressions.FunctionCall
 import prog8.ast.statements.FunctionCallStatement
 import prog8.ast.statements.Subroutine
@@ -16,7 +17,7 @@ internal class AstRecursionChecker(private val namespace: INameScope,
        if(cycle.isEmpty())
            return
        val chain = cycle.joinToString(" <-- ") { "${it.name} at ${it.position}" }
-        errors.err("Program contains recursive subroutine calls, this is not supported. Recursive chain:\n (a subroutine call in) $chain", null)
+        errors.err("Program contains recursive subroutine calls, this is not supported. Recursive chain:\n (a subroutine call in) $chain", Position.DUMMY)
    }

    override fun visit(functionCallStatement: FunctionCallStatement) {
@@ -0,0 +1,124 @@
+package prog8.ast.processing
+
+import prog8.ast.Node
+import prog8.ast.Program
+import prog8.ast.base.*
+import prog8.ast.expressions.*
+import prog8.ast.statements.*
+
+
+internal class AstVariousTransforms(private val program: Program) : AstWalker() {
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun before(decl: VarDecl, parent: Node): Iterable<IAstModification> {
+        // is it a struct variable? then define all its struct members as mangled names,
+        //    and include the original decl as well.
+        if(decl.datatype==DataType.STRUCT && !decl.structHasBeenFlattened) {
+            val decls = decl.flattenStructMembers()
+            decls.add(decl)
+            val result = AnonymousScope(decls, decl.position)
+            return listOf(IAstModification.ReplaceNode(
+                    decl, result, parent
+            ))
+        }
+
+        return noModifications
+    }
+
+    override fun after(subroutine: Subroutine, parent: Node): Iterable<IAstModification> {
+        // For non-kernel subroutines and non-asm parameters:
+        // inject subroutine params as local variables (if they're not there yet).
+        val symbolsInSub = subroutine.allDefinedSymbols()
+        val namesInSub = symbolsInSub.map{ it.first }.toSet()
+        if(subroutine.asmAddress==null) {
+            if(subroutine.asmParameterRegisters.isEmpty() && subroutine.parameters.isNotEmpty()) {
+                val vars = subroutine.statements.filterIsInstance<VarDecl>().map { it.name }.toSet()
+                if(!vars.containsAll(subroutine.parameters.map{it.name})) {
+                    return subroutine.parameters
+                            .filter { it.name !in namesInSub }
+                            .map {
+                                val vardecl = ParameterVarDecl(it.name, it.type, subroutine.position)
+                                IAstModification.InsertFirst(vardecl, subroutine)
+                            }
+                }
+            }
+        }
+
+        return noModifications
+    }
+
+    override fun before(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
+        when {
+            expr.left is StringLiteralValue ->
+                return listOf(IAstModification.ReplaceNode(
+                        expr,
+                        processBinaryExprWithString(expr.left as StringLiteralValue, expr.right, expr),
+                        parent
+                ))
+            expr.right is StringLiteralValue ->
+                return listOf(IAstModification.ReplaceNode(
+                        expr,
+                        processBinaryExprWithString(expr.right as StringLiteralValue, expr.left, expr),
+                        parent
+                ))
+        }
+
+        return noModifications
+    }
+
+    override fun after(string: StringLiteralValue, parent: Node): Iterable<IAstModification> {
+        if(string.parent !is VarDecl) {
+            // replace the literal string by a identifier reference to a new local vardecl
+            val vardecl = VarDecl.createAuto(string)
+            val identifier = IdentifierReference(listOf(vardecl.name), vardecl.position)
+            return listOf(
+                    IAstModification.ReplaceNode(string, identifier, parent),
+                    IAstModification.InsertFirst(vardecl, string.definingScope() as Node)
+            )
+        }
+        return noModifications
+    }
+
+    override fun after(array: ArrayLiteralValue, parent: Node): Iterable<IAstModification> {
+        val vardecl = array.parent as? VarDecl
+        if(vardecl!=null) {
+            // adjust the datatype of the array (to an educated guess)
+            val arrayDt = array.type
+            if(!arrayDt.istype(vardecl.datatype)) {
+                val cast = array.cast(vardecl.datatype)
+                if (cast != null && cast!=array)
+                    return listOf(IAstModification.ReplaceNode(vardecl.value!!, cast, vardecl))
+            }
+        } else {
+            val arrayDt = array.guessDatatype(program)
+            if(arrayDt.isKnown) {
+                // this array literal is part of an expression, turn it into an identifier reference
+                val litval2 = array.cast(arrayDt.typeOrElse(DataType.STRUCT))
+                if(litval2!=null && litval2!=array) {
+                    val vardecl2 = VarDecl.createAuto(litval2)
+                    val identifier = IdentifierReference(listOf(vardecl2.name), vardecl2.position)
+                    return listOf(
+                            IAstModification.ReplaceNode(array, identifier, parent),
+                            IAstModification.InsertFirst(vardecl2, array.definingScope() as Node)
+                    )
+                }
+            }
+        }
+        return noModifications
+    }
+
+    private fun processBinaryExprWithString(string: StringLiteralValue, operand: Expression, expr: BinaryExpression): Expression {
+        val constvalue = operand.constValue(program)
+        if(constvalue!=null) {
+            if (expr.operator == "*") {
+                // repeat a string a number of times
+                return StringLiteralValue(string.value.repeat(constvalue.number.toInt()), string.altEncoding, expr.position)
+            }
+        }
+        if(expr.operator == "+" && operand is StringLiteralValue) {
+            // concatenate two strings
+            return StringLiteralValue("${string.value}${operand.value}", string.altEncoding, expr.position)
+        }
+        return expr
+    }
+}
@@ -0,0 +1,442 @@
+package prog8.ast.processing
+
+import prog8.ast.*
+import prog8.ast.base.FatalAstException
+import prog8.ast.expressions.*
+import prog8.ast.statements.*
+
+
+interface IAstModification {
+    fun perform()
+
+    class Remove(val node: Node, val parent: Node) : IAstModification {
+        override fun perform() {
+            if(parent is INameScope) {
+                if (!parent.statements.remove(node) && parent !is GlobalNamespace)
+                    throw FatalAstException("attempt to remove non-existing node $node")
+            } else {
+                throw FatalAstException("parent of a remove modification is not an INameScope")
+            }
+        }
+    }
+
+    class SetExpression(val setter: (newExpr: Expression) -> Unit, val newExpr: Expression, val parent: Node) : IAstModification {
+        override fun perform() {
+            setter(newExpr)
+            newExpr.linkParents(parent)
+        }
+    }
+
+    class InsertFirst(val stmt: Statement, val parent: Node) : IAstModification {
+        override fun perform() {
+            if(parent is INameScope) {
+                parent.statements.add(0, stmt)
+                stmt.linkParents(parent)
+            } else {
+                throw FatalAstException("parent of an insert modification is not an INameScope")
+            }
+        }
+    }
+
+    class InsertLast(val stmt: Statement, val parent: Node) : IAstModification {
+        override fun perform() {
+            if(parent is INameScope) {
+                parent.statements.add(stmt)
+                stmt.linkParents(parent)
+            } else {
+                throw FatalAstException("parent of an insert modification is not an INameScope")
+            }
+        }
+    }
+
+    class InsertAfter(val after: Statement, val stmt: Statement, val parent: Node) : IAstModification {
+        override fun perform() {
+            if(parent is INameScope) {
+                val idx = parent.statements.indexOfFirst { it===after } + 1
+                parent.statements.add(idx, stmt)
+                stmt.linkParents(parent)
+            } else {
+                throw FatalAstException("parent of an insert modification is not an INameScope")
+            }
+        }
+    }
+
+    class InsertBefore(val before: Statement, val stmt: Statement, val parent: Node) : IAstModification {
+        override fun perform() {
+            if(parent is INameScope) {
+                val idx = parent.statements.indexOfFirst { it===before }
+                parent.statements.add(idx, stmt)
+                stmt.linkParents(parent)
+            } else {
+                throw FatalAstException("parent of an insert modification is not an INameScope")
+            }
+        }
+    }
+
+    class ReplaceNode(val node: Node, val replacement: Node, val parent: Node) : IAstModification {
+        override fun perform() {
+            parent.replaceChildNode(node, replacement)
+            replacement.linkParents(parent)
+        }
+    }
+
+    class SwapOperands(val expr: BinaryExpression): IAstModification {
+        override fun perform() {
+            val tmp = expr.left
+            expr.left = expr.right
+            expr.right = tmp
+        }
+    }
+}
+
+
+abstract class AstWalker {
+    open fun before(addressOf: AddressOf, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(array: ArrayLiteralValue, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(arrayIndexedExpression: ArrayIndexedExpression, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(assignTarget: AssignTarget, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(assignment: Assignment, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(block: Block, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(branchStatement: BranchStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(breakStmt: Break, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(builtinFunctionStatementPlaceholder: BuiltinFunctionStatementPlaceholder, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(decl: VarDecl, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(directive: Directive, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(expr: BinaryExpression, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(expr: PrefixExpression, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(forLoop: ForLoop, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(repeatLoop: RepeatLoop, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(functionCall: FunctionCall, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(functionCallStatement: FunctionCallStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(identifier: IdentifierReference, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(ifStatement: IfStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(inlineAssembly: InlineAssembly, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(jump: Jump, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(label: Label, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(memread: DirectMemoryRead, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(memwrite: DirectMemoryWrite, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(module: Module, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(nopStatement: NopStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(numLiteral: NumericLiteralValue, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(postIncrDecr: PostIncrDecr, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(program: Program, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(range: RangeExpr, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(untilLoop: UntilLoop, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(returnStmt: Return, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(scope: AnonymousScope, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(string: StringLiteralValue, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(structDecl: StructDecl, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(subroutine: Subroutine, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(whenChoice: WhenChoice, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(whenStatement: WhenStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun before(whileLoop: WhileLoop, parent: Node): Iterable<IAstModification> = emptyList()
+
+    open fun after(addressOf: AddressOf, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(array: ArrayLiteralValue, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(arrayIndexedExpression: ArrayIndexedExpression, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(assignTarget: AssignTarget, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(assignment: Assignment, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(block: Block, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(branchStatement: BranchStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(breakStmt: Break, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(builtinFunctionStatementPlaceholder: BuiltinFunctionStatementPlaceholder, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(directive: Directive, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(expr: BinaryExpression, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(expr: PrefixExpression, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(forLoop: ForLoop, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(repeatLoop: RepeatLoop, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(functionCall: FunctionCall, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(functionCallStatement: FunctionCallStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(identifier: IdentifierReference, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(ifStatement: IfStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(inlineAssembly: InlineAssembly, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(jump: Jump, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(label: Label, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(memread: DirectMemoryRead, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(memwrite: DirectMemoryWrite, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(module: Module, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(nopStatement: NopStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(numLiteral: NumericLiteralValue, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(postIncrDecr: PostIncrDecr, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(program: Program, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(range: RangeExpr, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(untilLoop: UntilLoop, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(returnStmt: Return, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(scope: AnonymousScope, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(string: StringLiteralValue, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(structDecl: StructDecl, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(subroutine: Subroutine, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(whenChoice: WhenChoice, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(whenStatement: WhenStatement, parent: Node): Iterable<IAstModification> = emptyList()
+    open fun after(whileLoop: WhileLoop, parent: Node): Iterable<IAstModification> = emptyList()
+
+    private val modifications = mutableListOf<Triple<IAstModification, Node, Node>>()
+
+    private fun track(mods: Iterable<IAstModification>, node: Node, parent: Node) {
+        for (it in mods) modifications += Triple(it, node, parent)
+    }
+
+    fun applyModifications(): Int {
+        modifications.forEach {
+            it.first.perform()
+        }
+        val amount = modifications.size
+        modifications.clear()
+        return amount
+    }
+
+    fun visit(program: Program) {
+        track(before(program, program), program, program)
+        program.modules.forEach { it.accept(this, program) }
+        track(after(program, program), program, program)
+    }
+
+    fun visit(module: Module, parent: Node) {
+        track(before(module, parent), module, parent)
+        module.statements.forEach{ it.accept(this, module) }
+        track(after(module, parent), module, parent)
+    }
+
+    fun visit(expr: PrefixExpression, parent: Node) {
+        track(before(expr, parent), expr, parent)
+        expr.expression.accept(this, expr)
+        track(after(expr, parent), expr, parent)
+    }
+
+    fun visit(expr: BinaryExpression, parent: Node) {
+        track(before(expr, parent), expr, parent)
+        expr.left.accept(this, expr)
+        expr.right.accept(this, expr)
+        track(after(expr, parent), expr, parent)
+    }
+
+    fun visit(directive: Directive, parent: Node) {
+        track(before(directive, parent), directive, parent)
+        track(after(directive, parent), directive, parent)
+    }
+
+    fun visit(block: Block, parent: Node) {
+        track(before(block, parent), block, parent)
+        block.statements.forEach { it.accept(this, block) }
+        track(after(block, parent), block, parent)
+    }
+
+    fun visit(decl: VarDecl, parent: Node) {
+        track(before(decl, parent), decl, parent)
+        decl.value?.accept(this, decl)
+        decl.arraysize?.accept(this, decl)
+        track(after(decl, parent), decl, parent)
+    }
+
+    fun visit(subroutine: Subroutine, parent: Node) {
+        track(before(subroutine, parent), subroutine, parent)
+        subroutine.statements.forEach { it.accept(this, subroutine) }
+        track(after(subroutine, parent), subroutine, parent)
+    }
+
+    fun visit(functionCall: FunctionCall, parent: Node) {
+        track(before(functionCall, parent), functionCall, parent)
+        functionCall.target.accept(this, functionCall)
+        functionCall.args.forEach { it.accept(this, functionCall) }
+        track(after(functionCall, parent), functionCall, parent)
+    }
+
+    fun visit(functionCallStatement: FunctionCallStatement, parent: Node) {
+        track(before(functionCallStatement, parent), functionCallStatement, parent)
+        functionCallStatement.target.accept(this, functionCallStatement)
+        functionCallStatement.args.forEach { it.accept(this, functionCallStatement) }
+        track(after(functionCallStatement, parent), functionCallStatement, parent)
+    }
+
+    fun visit(identifier: IdentifierReference, parent: Node) {
+        track(before(identifier, parent), identifier, parent)
+        track(after(identifier, parent), identifier, parent)
+    }
+
+    fun visit(jump: Jump, parent: Node) {
+        track(before(jump, parent), jump, parent)
+        jump.identifier?.accept(this, jump)
+        track(after(jump, parent), jump, parent)
+    }
+
+    fun visit(ifStatement: IfStatement, parent: Node) {
+        track(before(ifStatement, parent), ifStatement, parent)
+        ifStatement.condition.accept(this, ifStatement)
+        ifStatement.truepart.accept(this, ifStatement)
+        ifStatement.elsepart.accept(this, ifStatement)
+        track(after(ifStatement, parent), ifStatement, parent)
+    }
+
+    fun visit(branchStatement: BranchStatement, parent: Node) {
+        track(before(branchStatement, parent), branchStatement, parent)
+        branchStatement.truepart.accept(this, branchStatement)
+        branchStatement.elsepart.accept(this, branchStatement)
+        track(after(branchStatement, parent), branchStatement, parent)
+    }
+
+    fun visit(range: RangeExpr, parent: Node) {
+        track(before(range, parent), range, parent)
+        range.from.accept(this, range)
+        range.to.accept(this, range)
+        range.step.accept(this, range)
+        track(after(range, parent), range, parent)
+    }
+
+    fun visit(label: Label, parent: Node) {
+        track(before(label, parent), label, parent)
+        track(after(label, parent), label, parent)
+    }
+
+    fun visit(numLiteral: NumericLiteralValue, parent: Node) {
+        track(before(numLiteral, parent), numLiteral, parent)
+        track(after(numLiteral, parent), numLiteral, parent)
+    }
+
+    fun visit(string: StringLiteralValue, parent: Node) {
+        track(before(string, parent), string, parent)
+        track(after(string, parent), string, parent)
+    }
+
+    fun visit(array: ArrayLiteralValue, parent: Node) {
+        track(before(array, parent), array, parent)
+        array.value.forEach { v->v.accept(this, array) }
+        track(after(array, parent), array, parent)
+    }
+
+    fun visit(assignment: Assignment, parent: Node) {
+        track(before(assignment, parent), assignment, parent)
+        assignment.target.accept(this, assignment)
+        assignment.value.accept(this, assignment)
+        track(after(assignment, parent), assignment, parent)
+    }
+
+    fun visit(postIncrDecr: PostIncrDecr, parent: Node) {
+        track(before(postIncrDecr, parent), postIncrDecr, parent)
+        postIncrDecr.target.accept(this, postIncrDecr)
+        track(after(postIncrDecr, parent), postIncrDecr, parent)
+    }
+
+    fun visit(breakStmt: Break, parent: Node) {
+        track(before(breakStmt, parent), breakStmt, parent)
+        track(after(breakStmt, parent), breakStmt, parent)
+    }
+
+    fun visit(forLoop: ForLoop, parent: Node) {
+        track(before(forLoop, parent), forLoop, parent)
+        forLoop.loopVar.accept(this, forLoop)
+        forLoop.iterable.accept(this, forLoop)
+        forLoop.body.accept(this, forLoop)
+        track(after(forLoop, parent), forLoop, parent)
+    }
+
+    fun visit(whileLoop: WhileLoop, parent: Node) {
+        track(before(whileLoop, parent), whileLoop, parent)
+        whileLoop.condition.accept(this, whileLoop)
+        whileLoop.body.accept(this, whileLoop)
+        track(after(whileLoop, parent), whileLoop, parent)
+    }
+
+    fun visit(repeatLoop: RepeatLoop, parent: Node) {
+        track(before(repeatLoop, parent), repeatLoop, parent)
+        repeatLoop.iterations?.accept(this, repeatLoop)
+        repeatLoop.body.accept(this, repeatLoop)
+        track(after(repeatLoop, parent), repeatLoop, parent)
+    }
+
+    fun visit(untilLoop: UntilLoop, parent: Node) {
+        track(before(untilLoop, parent), untilLoop, parent)
+        untilLoop.untilCondition.accept(this, untilLoop)
+        untilLoop.body.accept(this, untilLoop)
+        track(after(untilLoop, parent), untilLoop, parent)
+    }
+
+    fun visit(returnStmt: Return, parent: Node) {
+        track(before(returnStmt, parent), returnStmt, parent)
+        returnStmt.value?.accept(this, returnStmt)
+        track(after(returnStmt, parent), returnStmt, parent)
+    }
+
+    fun visit(arrayIndexedExpression: ArrayIndexedExpression, parent: Node) {
+        track(before(arrayIndexedExpression, parent), arrayIndexedExpression, parent)
+        arrayIndexedExpression.identifier.accept(this, arrayIndexedExpression)
+        arrayIndexedExpression.arrayspec.accept(this, arrayIndexedExpression)
+        track(after(arrayIndexedExpression, parent), arrayIndexedExpression, parent)
+    }
+
+    fun visit(assignTarget: AssignTarget, parent: Node) {
+        track(before(assignTarget, parent), assignTarget, parent)
+        assignTarget.arrayindexed?.accept(this, assignTarget)
+        assignTarget.identifier?.accept(this, assignTarget)
+        assignTarget.memoryAddress?.accept(this, assignTarget)
+        track(after(assignTarget, parent), assignTarget, parent)
+    }
+
+    fun visit(scope: AnonymousScope, parent: Node) {
+        track(before(scope, parent), scope, parent)
+        scope.statements.forEach { it.accept(this, scope) }
+        track(after(scope, parent), scope, parent)
+    }
+
+    fun visit(typecast: TypecastExpression, parent: Node) {
+        track(before(typecast, parent), typecast, parent)
+        typecast.expression.accept(this, typecast)
+        track(after(typecast, parent), typecast, parent)
+    }
+
+    fun visit(memread: DirectMemoryRead, parent: Node) {
+        track(before(memread, parent), memread, parent)
+        memread.addressExpression.accept(this, memread)
+        track(after(memread, parent), memread, parent)
+    }
+
+    fun visit(memwrite: DirectMemoryWrite, parent: Node) {
+        track(before(memwrite, parent), memwrite, parent)
+        memwrite.addressExpression.accept(this, memwrite)
+        track(after(memwrite, parent), memwrite, parent)
+    }
+
+    fun visit(addressOf: AddressOf, parent: Node) {
+        track(before(addressOf, parent), addressOf, parent)
+        addressOf.identifier.accept(this, addressOf)
+        track(after(addressOf, parent), addressOf, parent)
+    }
+
+    fun visit(inlineAssembly: InlineAssembly, parent: Node) {
+        track(before(inlineAssembly, parent), inlineAssembly, parent)
+        track(after(inlineAssembly, parent), inlineAssembly, parent)
+    }
+
+    fun visit(builtinFunctionStatementPlaceholder: BuiltinFunctionStatementPlaceholder, parent: Node) {
+        track(before(builtinFunctionStatementPlaceholder, parent), builtinFunctionStatementPlaceholder, parent)
+        track(after(builtinFunctionStatementPlaceholder, parent), builtinFunctionStatementPlaceholder, parent)
+    }
+
+    fun visit(nopStatement: NopStatement, parent: Node) {
+        track(before(nopStatement, parent), nopStatement, parent)
+        track(after(nopStatement, parent), nopStatement, parent)
+    }
+
+    fun visit(whenStatement: WhenStatement, parent: Node) {
+        track(before(whenStatement, parent), whenStatement, parent)
+        whenStatement.condition.accept(this, whenStatement)
+        whenStatement.choices.forEach { it.accept(this, whenStatement) }
+        track(after(whenStatement, parent), whenStatement, parent)
+    }
+
+    fun visit(whenChoice: WhenChoice, parent: Node) {
+        track(before(whenChoice, parent), whenChoice, parent)
+        whenChoice.values?.forEach { it.accept(this, whenChoice) }
+        whenChoice.statements.accept(this, whenChoice)
+        track(after(whenChoice, parent), whenChoice, parent)
+    }
+
+    fun visit(structDecl: StructDecl, parent: Node) {
+        track(before(structDecl, parent), structDecl, parent)
+        structDecl.statements.forEach { it.accept(this, structDecl) }
+        track(after(structDecl, parent), structDecl, parent)
+    }
+}
+
@@ -1,267 +0,0 @@
-package prog8.ast.processing
-
-import prog8.ast.Module
-import prog8.ast.Program
-import prog8.ast.base.FatalAstException
-import prog8.ast.expressions.*
-import prog8.ast.statements.*
-
-
-interface IAstModifyingVisitor {
-    fun visit(program: Program) {
-        program.modules.forEach { visit(it) }
-    }
-
-    fun visit(module: Module) {
-        module.statements = module.statements.map { it.accept(this) }.toMutableList()
-    }
-
-    fun visit(expr: PrefixExpression): Expression {
-        expr.expression = expr.expression.accept(this)
-        return expr
-    }
-
-    fun visit(expr: BinaryExpression): Expression {
-        expr.left = expr.left.accept(this)
-        expr.right = expr.right.accept(this)
-        return expr
-    }
-
-    fun visit(directive: Directive): Statement {
-        return directive
-    }
-
-    fun visit(block: Block): Statement {
-        block.statements = block.statements.map { it.accept(this) }.toMutableList()
-        return block
-    }
-
-    fun visit(decl: VarDecl): Statement {
-        decl.value = decl.value?.accept(this)
-        decl.arraysize?.accept(this)
-        return decl
-    }
-
-    fun visit(subroutine: Subroutine): Statement {
-        subroutine.statements = subroutine.statements.map { it.accept(this) }.toMutableList()
-        return subroutine
-    }
-
-    fun visit(functionCall: FunctionCall): Expression {
-        val newtarget = functionCall.target.accept(this)
-        if(newtarget is IdentifierReference)
-            functionCall.target = newtarget
-        else
-            throw FatalAstException("cannot change class of function call target")
-        functionCall.args = functionCall.args.map { it.accept(this) }.toMutableList()
-        return functionCall
-    }
-
-    fun visit(functionCallStatement: FunctionCallStatement): Statement {
-        val newtarget = functionCallStatement.target.accept(this)
-        if(newtarget is IdentifierReference)
-            functionCallStatement.target = newtarget
-        else
-            throw FatalAstException("cannot change class of function call target")
-        functionCallStatement.args = functionCallStatement.args.map { it.accept(this) }.toMutableList()
-        return functionCallStatement
-    }
-
-    fun visit(identifier: IdentifierReference): Expression {
-        // note: this is an identifier that is used in an expression.
-        // other identifiers are simply part of the other statements (such as jumps, subroutine defs etc)
-        return identifier
-    }
-
-    fun visit(jump: Jump): Statement {
-        if(jump.identifier!=null) {
-            val ident = jump.identifier.accept(this)
-            if(ident is IdentifierReference && ident!==jump.identifier) {
-                return Jump(null, ident, null, jump.position)
-            }
-        }
-        return jump
-    }
-
-    fun visit(ifStatement: IfStatement): Statement {
-        ifStatement.condition = ifStatement.condition.accept(this)
-        ifStatement.truepart = ifStatement.truepart.accept(this) as AnonymousScope
-        ifStatement.elsepart = ifStatement.elsepart.accept(this) as AnonymousScope
-        return ifStatement
-    }
-
-    fun visit(branchStatement: BranchStatement): Statement {
-        branchStatement.truepart = branchStatement.truepart.accept(this) as AnonymousScope
-        branchStatement.elsepart = branchStatement.elsepart.accept(this) as AnonymousScope
-        return branchStatement
-    }
-
-    fun visit(range: RangeExpr): Expression {
-        range.from = range.from.accept(this)
-        range.to = range.to.accept(this)
-        range.step = range.step.accept(this)
-        return range
-    }
-
-    fun visit(label: Label): Statement {
-        return label
-    }
-
-    fun visit(literalValue: NumericLiteralValue): NumericLiteralValue {
-        return literalValue
-    }
-
-    fun visit(stringLiteral: StringLiteralValue): Expression {
-        return stringLiteral
-    }
-
-    fun visit(arrayLiteral: ArrayLiteralValue): Expression {
-        for(av in arrayLiteral.value.withIndex()) {
-            val newvalue = av.value.accept(this)
-            arrayLiteral.value[av.index] = newvalue
-        }
-        return arrayLiteral
-    }
-
-    fun visit(assignment: Assignment): Statement {
-        assignment.target = assignment.target.accept(this)
-        assignment.value = assignment.value.accept(this)
-        return assignment
-    }
-
-    fun visit(postIncrDecr: PostIncrDecr): Statement {
-        postIncrDecr.target = postIncrDecr.target.accept(this)
-        return postIncrDecr
-    }
-
-    fun visit(contStmt: Continue): Statement {
-        return contStmt
-    }
-
-    fun visit(breakStmt: Break): Statement {
-        return breakStmt
-    }
-
-    fun visit(forLoop: ForLoop): Statement {
-        when(val newloopvar = forLoop.loopVar?.accept(this)) {
-            is IdentifierReference -> forLoop.loopVar = newloopvar
-            null -> forLoop.loopVar = null
-            else -> throw FatalAstException("can't change class of loopvar")
-        }
-        forLoop.iterable = forLoop.iterable.accept(this)
-        forLoop.body = forLoop.body.accept(this) as AnonymousScope
-        return forLoop
-    }
-
-    fun visit(whileLoop: WhileLoop): Statement {
-        whileLoop.condition = whileLoop.condition.accept(this)
-        whileLoop.body = whileLoop.body.accept(this) as AnonymousScope
-        return whileLoop
-    }
-
-    fun visit(foreverLoop: ForeverLoop): Statement {
-        foreverLoop.body = foreverLoop.body.accept(this) as AnonymousScope
-        return foreverLoop
-    }
-
-    fun visit(repeatLoop: RepeatLoop): Statement {
-        repeatLoop.untilCondition = repeatLoop.untilCondition.accept(this)
-        repeatLoop.body = repeatLoop.body.accept(this) as AnonymousScope
-        return repeatLoop
-    }
-
-    fun visit(returnStmt: Return): Statement {
-        returnStmt.value = returnStmt.value?.accept(this)
-        return returnStmt
-    }
-
-    fun visit(arrayIndexedExpression: ArrayIndexedExpression): ArrayIndexedExpression {
-        val ident = arrayIndexedExpression.identifier.accept(this)
-        if(ident is IdentifierReference)
-            arrayIndexedExpression.identifier = ident
-        arrayIndexedExpression.arrayspec.accept(this)
-        return arrayIndexedExpression
-    }
-
-    fun visit(assignTarget: AssignTarget): AssignTarget {
-        when (val ident = assignTarget.identifier?.accept(this)) {
-            is IdentifierReference -> assignTarget.identifier = ident
-            null -> assignTarget.identifier = null
-            else -> throw FatalAstException("can't change class of assign target identifier")
-        }
-        assignTarget.arrayindexed = assignTarget.arrayindexed?.accept(this)
-        assignTarget.memoryAddress?.let { visit(it) }
-        return assignTarget
-    }
-
-    fun visit(scope: AnonymousScope): Statement {
-        scope.statements = scope.statements.map { it.accept(this) }.toMutableList()
-        return scope
-    }
-
-    fun visit(typecast: TypecastExpression): Expression {
-        typecast.expression = typecast.expression.accept(this)
-        return typecast
-    }
-
-    fun visit(memread: DirectMemoryRead): Expression {
-        memread.addressExpression = memread.addressExpression.accept(this)
-        return memread
-    }
-
-    fun visit(memwrite: DirectMemoryWrite) {
-        memwrite.addressExpression = memwrite.addressExpression.accept(this)
-    }
-
-    fun visit(addressOf: AddressOf): Expression {
-        val ident = addressOf.identifier.accept(this)
-        if(ident is IdentifierReference)
-            addressOf.identifier = ident
-        else
-            throw FatalAstException("can't change class of addressof identifier")
-        return addressOf
-    }
-
-    fun visit(inlineAssembly: InlineAssembly): Statement {
-        return inlineAssembly
-    }
-
-    fun visit(registerExpr: RegisterExpr): Expression {
-        return registerExpr
-    }
-
-    fun visit(builtinFunctionStatementPlaceholder: BuiltinFunctionStatementPlaceholder): Statement {
-        return builtinFunctionStatementPlaceholder
-    }
-
-    fun visit(nopStatement: NopStatement): Statement {
-        return nopStatement
-    }
-
-    fun visit(whenStatement: WhenStatement): Statement {
-        whenStatement.condition = whenStatement.condition.accept(this)
-        whenStatement.choices.forEach { it.accept(this) }
-        return whenStatement
-    }
-
-    fun visit(whenChoice: WhenChoice) {
-        whenChoice.values = whenChoice.values?.map { it.accept(this) }
-        val stmt = whenChoice.statements.accept(this)
-        if(stmt is AnonymousScope)
-            whenChoice.statements = stmt
-        else {
-            whenChoice.statements = AnonymousScope(mutableListOf(stmt), stmt.position)
-            whenChoice.statements.linkParents(whenChoice)
-        }
-    }
-
-    fun visit(structDecl: StructDecl): Statement {
-        structDecl.statements = structDecl.statements.map{ it.accept(this) }.toMutableList()
-        return structDecl
-    }
-
-    fun visit(structLv: StructLiteralValue): Expression {
-        structLv.values = structLv.values.map { it.accept(this) }
-        return structLv
-    }
-}
@@ -7,7 +7,7 @@ import prog8.ast.statements.*

 interface IAstVisitor {
    fun visit(program: Program) {
-        program.modules.forEach { visit(it) }
+        program.modules.forEach { it.accept(this) }
    }

    fun visit(module: Module) {
@@ -95,14 +95,11 @@ interface IAstVisitor {
        postIncrDecr.target.accept(this)
    }

-    fun visit(contStmt: Continue) {
-    }
-
    fun visit(breakStmt: Break) {
    }

    fun visit(forLoop: ForLoop) {
-        forLoop.loopVar?.accept(this)
+        forLoop.loopVar.accept(this)
        forLoop.iterable.accept(this)
        forLoop.body.accept(this)
    }
@@ -112,13 +109,14 @@ interface IAstVisitor {
        whileLoop.body.accept(this)
    }

-    fun visit(foreverLoop: ForeverLoop) {
-        foreverLoop.body.accept(this)
+    fun visit(repeatLoop: RepeatLoop) {
+        repeatLoop.iterations?.accept(this)
+        repeatLoop.body.accept(this)
    }

-    fun visit(repeatLoop: RepeatLoop) {
-        repeatLoop.untilCondition.accept(this)
-        repeatLoop.body.accept(this)
+    fun visit(untilLoop: UntilLoop) {
+        untilLoop.untilCondition.accept(this)
+        untilLoop.body.accept(this)
    }

    fun visit(returnStmt: Return) {
@@ -159,9 +157,6 @@ interface IAstVisitor {
    fun visit(inlineAssembly: InlineAssembly) {
    }

-    fun visit(registerExpr: RegisterExpr) {
-    }
-
    fun visit(builtinFunctionStatementPlaceholder: BuiltinFunctionStatementPlaceholder) {
    }

@@ -181,8 +176,4 @@ interface IAstVisitor {
    fun visit(structDecl: StructDecl) {
        structDecl.statements.forEach { it.accept(this) }
    }
-
-    fun visit(structLv: StructLiteralValue) {
-        structLv.values.forEach { it.accept(this) }
-    }
 }
@@ -1,29 +1,21 @@
 package prog8.ast.processing

-import prog8.ast.Module
-import prog8.ast.base.ErrorReporter
+import prog8.ast.Node
 import prog8.ast.statements.Directive
-import prog8.ast.statements.Statement

-internal class ImportedModuleDirectiveRemover(private val errors: ErrorReporter) : IAstModifyingVisitor {
+
+internal class ImportedModuleDirectiveRemover: AstWalker() {
    /**
     * Most global directives don't apply for imported modules, so remove them
     */
-    override fun visit(module: Module) {
-        super.visit(module)
-        val newStatements : MutableList<Statement> = mutableListOf()

-        val moduleLevelDirectives = listOf("%output", "%launcher", "%zeropage", "%zpreserved", "%address")
-        for (sourceStmt in module.statements) {
-            val stmt = sourceStmt.accept(this)
-            if(stmt is Directive && stmt.parent is Module) {
-                if(stmt.directive in moduleLevelDirectives) {
-                    errors.warn("ignoring module directive because it was imported", stmt.position)
-                    continue
-                }
-            }
-            newStatements.add(stmt)
+    private val moduleLevelDirectives = listOf("%output", "%launcher", "%zeropage", "%zpreserved", "%address")
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun before(directive: Directive, parent: Node): Iterable<IAstModification> {
+        if(directive.directive in moduleLevelDirectives) {
+            return listOf(IAstModification.Remove(directive, parent))
        }
-        module.statements = newStatements
+        return noModifications
    }
 }
@@ -1,24 +0,0 @@
-package prog8.ast.processing
-
-import prog8.ast.expressions.NumericLiteralValue
-import prog8.ast.statements.ForeverLoop
-import prog8.ast.statements.RepeatLoop
-import prog8.ast.statements.Statement
-import prog8.ast.statements.WhileLoop
-
-internal class MakeForeverLoops : IAstModifyingVisitor {
-    override fun visit(whileLoop: WhileLoop): Statement {
-        val numeric = whileLoop.condition as? NumericLiteralValue
-        if(numeric!=null && numeric.number.toInt() != 0) {
-            return ForeverLoop(whileLoop.body, whileLoop.position)
-        }
-        return super.visit(whileLoop)
-    }
-
-    override fun visit(repeatLoop: RepeatLoop): Statement {
-        val numeric = repeatLoop.untilCondition as? NumericLiteralValue
-        if(numeric!=null && numeric.number.toInt() == 0)
-            return ForeverLoop(repeatLoop.body, repeatLoop.position)
-        return super.visit(repeatLoop)
-    }
-}
@@ -0,0 +1,71 @@
+package prog8.ast.processing
+
+
+/*
+This is here for reference only, reflection based ast walking is very slow
+when compared to the more verbose visitor pattern interfaces.
+Too bad, because the code is very small
+*/
+
+
+//import prog8.ast.NoAstWalk
+//import prog8.ast.Node
+//import prog8.ast.Program
+//import prog8.ast.base.Position
+//import prog8.ast.expressions.BinaryExpression
+//import prog8.ast.expressions.NumericLiteralValue
+//import kotlin.reflect.KClass
+//import kotlin.reflect.KVisibility
+//import kotlin.reflect.full.declaredMemberProperties
+//import kotlin.reflect.full.isSubtypeOf
+//import kotlin.reflect.full.starProjectedType
+//
+//
+//class ReflectionAstWalker {
+//    private val nodeType = Node::class.starProjectedType
+//    private val collectionType = Collection::class.starProjectedType
+//
+//
+//    fun walk(node: Node, nesting: Int) {
+//        val nodetype: KClass<out Node> = node::class
+//        val indent = "  ".repeat(nesting)
+//        //println("$indent VISITING ${nodetype.simpleName}")
+//        val visibleAstMembers = nodetype.declaredMemberProperties.filter {
+//            it.visibility!=KVisibility.PRIVATE && !it.isLateinit &&
+//                    !(it.annotations.any{a->a is NoAstWalk})
+//        }
+//        for(prop in visibleAstMembers) {
+//            if(prop.returnType.isSubtypeOf(nodeType)) {
+//                // println("$indent +PROP: ${prop.name}")
+//                walk(prop.call(node) as Node, nesting + 1)
+//            }
+//            else if(prop.returnType.isSubtypeOf(collectionType)) {
+//                val elementType = prop.returnType.arguments.single().type
+//                if(elementType!=null && elementType.isSubtypeOf(nodeType)) {
+//                    val nodes = prop.call(node) as Collection<Node>
+//                    nodes.forEach { walk(it, nesting+1) }
+//                }
+//            }
+//        }
+//    }
+//    fun walk(program: Program) {
+//        for(module in program.modules) {
+//            println("---MODULE $module---")
+//            walk(module, 0)
+//        }
+//    }
+//}
+//
+//
+//fun main() {
+//    val ast = BinaryExpression(
+//            NumericLiteralValue.optimalInteger(100, Position.DUMMY),
+//            "+",
+//            NumericLiteralValue.optimalInteger(200, Position.DUMMY),
+//            Position.DUMMY
+//    )
+//
+//    val walker = ReflectionAstWalker()
+//    walker.walk(ast,0)
+//
+//}
@@ -1,257 +1,211 @@
 package prog8.ast.processing

 import prog8.ast.*
-import prog8.ast.base.DataType
-import prog8.ast.base.FatalAstException
-import prog8.ast.base.initvarsSubName
+import prog8.ast.base.*
 import prog8.ast.expressions.*
 import prog8.ast.statements.*


-private fun flattenStructAssignmentFromIdentifier(structAssignment: Assignment, program: Program): List<Assignment> {
-    val identifier = structAssignment.target.identifier!!
-    val identifierName = identifier.nameInSource.single()
-    val targetVar = identifier.targetVarDecl(program.namespace)!!
-    val struct = targetVar.struct!!
-    when (structAssignment.value) {
-        is IdentifierReference -> {
-            val sourceVar = (structAssignment.value as IdentifierReference).targetVarDecl(program.namespace)!!
-            if (sourceVar.struct == null)
-                throw FatalAstException("can only assign arrays or structs to structs")
-            // struct memberwise copy
-            val sourceStruct = sourceVar.struct!!
-            if(sourceStruct!==targetVar.struct) {
-                // structs are not the same in assignment
-                return listOf()     // error will be printed elsewhere
-            }
-            return struct.statements.zip(sourceStruct.statements).map { member ->
-                val targetDecl = member.first as VarDecl
-                val sourceDecl = member.second as VarDecl
-                if(targetDecl.name != sourceDecl.name)
-                    throw FatalAstException("struct member mismatch")
-                val mangled = mangledStructMemberName(identifierName, targetDecl.name)
-                val idref = IdentifierReference(listOf(mangled), structAssignment.position)
-                val sourcemangled = mangledStructMemberName(sourceVar.name, sourceDecl.name)
-                val sourceIdref = IdentifierReference(listOf(sourcemangled), structAssignment.position)
-                val assign = Assignment(AssignTarget(null, idref, null, null, structAssignment.position),
-                        null, sourceIdref, member.second.position)
-                assign.linkParents(structAssignment)
-                assign
-            }
-        }
-        is StructLiteralValue -> {
-            throw IllegalArgumentException("not going to flatten a structLv assignment here")
-        }
-        else -> throw FatalAstException("strange struct value")
-    }
-}
-
-
-internal class StatementReorderer(private val program: Program): IAstModifyingVisitor {
+internal class StatementReorderer(val program: Program) : AstWalker() {
    // Reorders the statements in a way the compiler needs.
    // - 'main' block must be the very first statement UNLESS it has an address set.
-    // - blocks are ordered by address, where blocks without address are put at the end.
-    // - in every scope:
-    //      -- the directives '%output', '%launcher', '%zeropage', '%zpreserved', '%address' and '%option' will come first.
-    //      -- all vardecls then follow.
-    //      -- the remaining statements then follow in their original order.
-    //
-    // - the 'start' subroutine in the 'main' block will be moved to the top immediately following the directives.
-    // - all other subroutines will be moved to the end of their block.
+    // - library blocks are put last.
+    // - blocks are ordered by address, where blocks without address are placed last.
+    // - in every scope, most directives and vardecls are moved to the top.
+    // - the 'start' subroutine is moved to the top.
+    // - (syntax desugaring) a vardecl with a non-const initializer value is split into a regular vardecl and an assignment statement.
+    // - (syntax desugaring) struct value assignment is expanded into several struct member assignments.
+    // - in-place assignments are reordered a bit so that they are mostly of the form A = A <operator> <rest>
    // - sorts the choices in when statement.
+    // - insert AddressOf (&) expression where required (string params to a UWORD function param etc).

+    private val noModifications = emptyList<IAstModification>()
    private val directivesToMove = setOf("%output", "%launcher", "%zeropage", "%zpreserved", "%address", "%option")

-    private val addReturns = mutableListOf<Pair<INameScope, Int>>()
-
-    override fun visit(module: Module) {
-        addReturns.clear()
-        super.visit(module)
-
+    override fun after(module: Module, parent: Node): Iterable<IAstModification> {
        val (blocks, other) = module.statements.partition { it is Block }
        module.statements = other.asSequence().plus(blocks.sortedBy { (it as Block).address ?: Int.MAX_VALUE }).toMutableList()

-        // make sure user-defined blocks come BEFORE library blocks, and move the "main" block to the top of everything
-        val nonLibraryBlocks = module.statements.withIndex()
-                .filter { it.value is Block && !(it.value as Block).isInLibrary }
-                .map { it.index to it.value }
-                .reversed()
-        for(nonLibBlock in nonLibraryBlocks)
-            module.statements.removeAt(nonLibBlock.first)
-        for(nonLibBlock in nonLibraryBlocks)
-            module.statements.add(0, nonLibBlock.second)
-        val mainBlock = module.statements.singleOrNull { it is Block && it.name=="main" }
-        if(mainBlock!=null && (mainBlock as Block).address==null) {
-            module.remove(mainBlock)
+        val mainBlock = module.statements.filterIsInstance<Block>().firstOrNull { it.name=="main" }
+        if(mainBlock!=null && mainBlock.address==null) {
+            module.statements.remove(mainBlock)
            module.statements.add(0, mainBlock)
        }

-        val varDecls = module.statements.filterIsInstance<VarDecl>()
-        module.statements.removeAll(varDecls)
-        module.statements.addAll(0, varDecls)
-
-        val directives = module.statements.filter {it is Directive && it.directive in directivesToMove}
-        module.statements.removeAll(directives)
-        module.statements.addAll(0, directives)
-
-        for(pos in addReturns) {
-            val returnStmt = Return(null, pos.first.position)
-            returnStmt.linkParents(pos.first as Node)
-            pos.first.statements.add(pos.second, returnStmt)
-        }
+        reorderVardeclsAndDirectives(module.statements)
+        return noModifications
    }

-    override fun visit(block: Block): Statement {
+    private fun reorderVardeclsAndDirectives(statements: MutableList<Statement>) {
+        val varDecls = statements.filterIsInstance<VarDecl>()
+        statements.removeAll(varDecls)
+        statements.addAll(0, varDecls)

-        val subroutines = block.statements.filterIsInstance<Subroutine>()
-        var numSubroutinesAtEnd = 0
-        // move all subroutines to the end of the block
-        for (subroutine in subroutines) {
-            if(subroutine.name!="start" || block.name!="main") {
-                block.remove(subroutine)
-                block.statements.add(subroutine)
-            }
-            numSubroutinesAtEnd++
+        val directives = statements.filterIsInstance<Directive>().filter {it.directive in directivesToMove}
+        statements.removeAll(directives)
+        statements.addAll(0, directives)
+    }
+
+    override fun before(block: Block, parent: Node): Iterable<IAstModification> {
+        parent as Module
+        if(block.isInLibrary) {
+            return listOf(
+                    IAstModification.Remove(block, parent),
+                    IAstModification.InsertLast(block, parent)
+            )
        }
-        // move the "start" subroutine to the top
-        if(block.name=="main") {
-            block.statements.singleOrNull { it is Subroutine && it.name == "start" } ?.let {
-                block.remove(it)
-                block.statements.add(0, it)
-                numSubroutinesAtEnd--
+
+        reorderVardeclsAndDirectives(block.statements)
+        return noModifications
+    }
+
+    override fun before(subroutine: Subroutine, parent: Node): Iterable<IAstModification> {
+        if(subroutine.name=="start" && parent is Block) {
+            if(parent.statements.filterIsInstance<Subroutine>().first().name!="start") {
+                return listOf(
+                        IAstModification.Remove(subroutine, parent),
+                        IAstModification.InsertFirst(subroutine, parent)
+                )
+            }
+        }
+        return noModifications
+    }
+
+
+    override fun after(whenStatement: WhenStatement, parent: Node): Iterable<IAstModification> {
+        val choices = whenStatement.choiceValues(program).sortedBy {
+            it.first?.first() ?: Int.MAX_VALUE
+        }
+        whenStatement.choices.clear()
+        choices.mapTo(whenStatement.choices) { it.second }
+        return noModifications
+    }
+
+    override fun before(assignment: Assignment, parent: Node): Iterable<IAstModification> {
+        val valueType = assignment.value.inferType(program)
+        val targetType = assignment.target.inferType(program, assignment)
+        if(valueType.istype(DataType.STRUCT) && targetType.istype(DataType.STRUCT)) {
+            val assignments = if (assignment.value is ArrayLiteralValue) {
+                flattenStructAssignmentFromStructLiteral(assignment, program)    //  'structvar = [ ..... ] '
+            } else {
+                flattenStructAssignmentFromIdentifier(assignment, program)    //   'structvar1 = structvar2'
+            }
+            if(assignments.isNotEmpty()) {
+                val modifications = mutableListOf<IAstModification>()
+                assignments.reversed().mapTo(modifications) { IAstModification.InsertAfter(assignment, it, parent) }
+                modifications.add(IAstModification.Remove(assignment, parent))
+                return modifications
            }
        }

-        // make sure there is a 'return' in front of the first subroutine
-        // (if it isn't the first statement in the block itself, and isn't the program's entrypoint)
-        if(numSubroutinesAtEnd>0 && block.statements.size > (numSubroutinesAtEnd+1)) {
-            val firstSub = block.statements[block.statements.size - numSubroutinesAtEnd] as Subroutine
-            if(firstSub.name != "start" && block.name != "main") {
-                val stmtBeforeFirstSub = block.statements[block.statements.size - numSubroutinesAtEnd - 1]
-                if (stmtBeforeFirstSub !is Return
-                        && stmtBeforeFirstSub !is Jump
-                        && stmtBeforeFirstSub !is Subroutine
-                        && stmtBeforeFirstSub !is BuiltinFunctionStatementPlaceholder) {
-                    val ret = Return(null, stmtBeforeFirstSub.position)
-                    ret.linkParents(block)
-                    block.statements.add(block.statements.size - numSubroutinesAtEnd, ret)
+        return noModifications
+    }
+
+    override fun after(assignment: Assignment, parent: Node): Iterable<IAstModification> {
+        // rewrite in-place assignment expressions a bit so that the assignment target usually is the leftmost operand
+        val binExpr = assignment.value as? BinaryExpression
+        if(binExpr!=null) {
+            if(binExpr.left isSameAs assignment.target) {
+                // A = A <operator> 5, unchanged
+                return noModifications
+            }
+
+            if(binExpr.operator in associativeOperators) {
+                if (binExpr.right isSameAs assignment.target) {
+                    // A = v <associative-operator> A  ==>  A = A <associative-operator> v
+                    return listOf(IAstModification.SwapOperands(binExpr))
                }
-            }
-        }

-        val varDecls = block.statements.filterIsInstance<VarDecl>()
-        block.statements.removeAll(varDecls)
-        block.statements.addAll(0, varDecls)
-        val directives = block.statements.filter {it is Directive && it.directive in directivesToMove}
-        block.statements.removeAll(directives)
-        block.statements.addAll(0, directives)
-        block.linkParents(block.parent)
-
-        // create subroutine that initializes the block's variables (if any)
-        val varInits = block.statements.withIndex().filter { it.value is VariableInitializationAssignment }
-        if(varInits.isNotEmpty()) {
-            val statements = varInits.map{it.value}.toMutableList()
-            val varInitSub = Subroutine(initvarsSubName, emptyList(), emptyList(), emptyList(), emptyList(),
-                    emptySet(), null, false, statements, block.position)
-            varInitSub.keepAlways = true
-            varInitSub.linkParents(block)
-            block.statements.add(varInitSub)
-
-            // remove the varinits from the block's statements
-            for(index in varInits.map{it.index}.reversed())
-                block.statements.removeAt(index)
-        }
-
-        return super.visit(block)
-    }
-
-    override fun visit(subroutine: Subroutine): Statement {
-        super.visit(subroutine)
-
-        val scope = subroutine.definingScope()
-        if(scope is Subroutine) {
-            for(stmt in scope.statements.withIndex()) {
-                if(stmt.index>0 && stmt.value===subroutine) {
-                    val precedingStmt = scope.statements[stmt.index-1]
-                    if(precedingStmt !is Jump && precedingStmt !is Subroutine) {
-                        // insert a return statement before a nested subroutine, to avoid falling trough inside the subroutine
-                        addReturns.add(Pair(scope, stmt.index))
+                val leftBinExpr = binExpr.left as? BinaryExpression
+                if(leftBinExpr?.operator == binExpr.operator) {
+                    return if(leftBinExpr.left isSameAs assignment.target) {
+                        // A = (A <associative-operator> x) <same-operator> y ==> A = A <associative-operator> (x <same-operator> y)
+                        val newRight = BinaryExpression(leftBinExpr.right, binExpr.operator, binExpr.right, binExpr.position)
+                        val newValue = BinaryExpression(leftBinExpr.left, binExpr.operator, newRight, binExpr.position)
+                        listOf(IAstModification.ReplaceNode(binExpr, newValue, assignment))
+                    } else {
+                        // A = (x <associative-operator> A) <same-operator> y ==> A = A <associative-operator> (x <same-operator> y)
+                        val newRight = BinaryExpression(leftBinExpr.left, binExpr.operator, binExpr.right, binExpr.position)
+                        val newValue = BinaryExpression(leftBinExpr.right, binExpr.operator, newRight, binExpr.position)
+                        listOf(IAstModification.ReplaceNode(binExpr, newValue, assignment))
+                    }
+                }
+                val rightBinExpr = binExpr.right as? BinaryExpression
+                if(rightBinExpr?.operator == binExpr.operator) {
+                    return if(rightBinExpr.left isSameAs assignment.target) {
+                        // A = x <associative-operator> (A <same-operator> y) ==> A = A <associative-operator> (x <same-operator> y)
+                        val newRight = BinaryExpression(binExpr.left, binExpr.operator, rightBinExpr.right, binExpr.position)
+                        val newValue = BinaryExpression(rightBinExpr.left, binExpr.operator, newRight, binExpr.position)
+                        listOf(IAstModification.ReplaceNode(binExpr, newValue, assignment))
+                    } else {
+                        // A = x <associative-operator> (y <same-operator> A) ==> A = A <associative-operator> (x <same-operator> y)
+                        val newRight = BinaryExpression(binExpr.left, binExpr.operator, rightBinExpr.left, binExpr.position)
+                        val newValue = BinaryExpression(rightBinExpr.right, binExpr.operator, newRight, binExpr.position)
+                        listOf(IAstModification.ReplaceNode(binExpr, newValue, assignment))
                    }
                }
            }
        }

-        val varDecls = subroutine.statements.filterIsInstance<VarDecl>()
-        subroutine.statements.removeAll(varDecls)
-        subroutine.statements.addAll(0, varDecls)
-        val directives = subroutine.statements.filter {it is Directive && it.directive in directivesToMove}
-        subroutine.statements.removeAll(directives)
-        subroutine.statements.addAll(0, directives)
-
-        if(subroutine.returntypes.isEmpty()) {
-            // add the implicit return statement at the end (if it's not there yet), but only if it's not a kernel routine.
-            // and if an assembly block doesn't contain a rts/rti
-            if(subroutine.asmAddress==null && subroutine.amountOfRtsInAsm()==0) {
-                if (subroutine.statements.lastOrNull {it !is VarDecl } !is Return) {
-                    val returnStmt = Return(null, subroutine.position)
-                    returnStmt.linkParents(subroutine)
-                    subroutine.statements.add(returnStmt)
-                }
-            }
-        }
-
-        return subroutine
+        return noModifications
    }

-    override fun visit(assignment: Assignment): Statement {
-        val assg = super.visit(assignment)
-        if(assg !is Assignment)
-            return assg
+    private fun flattenStructAssignmentFromStructLiteral(structAssignment: Assignment, program: Program): List<Assignment> {
+        val identifier = structAssignment.target.identifier!!
+        val identifierName = identifier.nameInSource.single()
+        val targetVar = identifier.targetVarDecl(program.namespace)!!
+        val struct = targetVar.struct!!

-        // see if a typecast is needed to convert the value's type into the proper target type
-        val valueItype = assg.value.inferType(program)
-        val targetItype = assg.target.inferType(program, assg)
+        val slv = structAssignment.value as? ArrayLiteralValue
+        if(slv==null || slv.value.size != struct.numberOfElements)
+            throw FatalAstException("element count mismatch")

-        if(targetItype.isKnown && valueItype.isKnown) {
-            val targettype = targetItype.typeOrElse(DataType.STRUCT)
-            val valuetype = valueItype.typeOrElse(DataType.STRUCT)
+        return struct.statements.zip(slv.value).map { (targetDecl, sourceValue) ->
+            targetDecl as VarDecl
+            val mangled = mangledStructMemberName(identifierName, targetDecl.name)
+            val idref = IdentifierReference(listOf(mangled), structAssignment.position)
+            val assign = Assignment(AssignTarget(idref, null, null, structAssignment.position),
+                    sourceValue, sourceValue.position)
+            assign.linkParents(structAssignment)
+            assign
+        }
+    }

-            // struct assignments will be flattened (if it's not a struct literal)
-            if (valuetype == DataType.STRUCT && targettype == DataType.STRUCT) {
-                if (assg.value is StructLiteralValue)
-                    return assg  // do NOT flatten it at this point!! (the compiler will take care if it, later, if needed)
-
-                val assignments = flattenStructAssignmentFromIdentifier(assg, program)    //   'structvar1 = structvar2'
-                return if (assignments.isEmpty()) {
-                    // something went wrong (probably incompatible struct types)
-                    // we'll get an error later from the AstChecker
-                    assg
-                } else {
-                    val scope = AnonymousScope(assignments.toMutableList(), assg.position)
-                    scope.linkParents(assg.parent)
-                    scope
+    private fun flattenStructAssignmentFromIdentifier(structAssignment: Assignment, program: Program): List<Assignment> {
+        val identifier = structAssignment.target.identifier!!
+        val identifierName = identifier.nameInSource.single()
+        val targetVar = identifier.targetVarDecl(program.namespace)!!
+        val struct = targetVar.struct!!
+        when (structAssignment.value) {
+            is IdentifierReference -> {
+                val sourceVar = (structAssignment.value as IdentifierReference).targetVarDecl(program.namespace)!!
+                if (sourceVar.struct == null)
+                    throw FatalAstException("can only assign arrays or structs to structs")
+                // struct memberwise copy
+                val sourceStruct = sourceVar.struct!!
+                if(sourceStruct!==targetVar.struct) {
+                    // structs are not the same in assignment
+                    return listOf()     // error will be printed elsewhere
+                }
+                return struct.statements.zip(sourceStruct.statements).map { member ->
+                    val targetDecl = member.first as VarDecl
+                    val sourceDecl = member.second as VarDecl
+                    if(targetDecl.name != sourceDecl.name)
+                        throw FatalAstException("struct member mismatch")
+                    val mangled = mangledStructMemberName(identifierName, targetDecl.name)
+                    val idref = IdentifierReference(listOf(mangled), structAssignment.position)
+                    val sourcemangled = mangledStructMemberName(sourceVar.name, sourceDecl.name)
+                    val sourceIdref = IdentifierReference(listOf(sourcemangled), structAssignment.position)
+                    val assign = Assignment(AssignTarget(idref, null, null, structAssignment.position), sourceIdref, member.second.position)
+                    assign.linkParents(structAssignment)
+                    assign
                }
            }
+            is ArrayLiteralValue -> {
+                throw IllegalArgumentException("not going to flatten a structLv assignment here")
+            }
+            else -> throw FatalAstException("strange struct value")
        }
-
-        if(assg.aug_op!=null) {
-            // transform augmented assg into normal assg so we have one case less to deal with later
-            val newTarget: Expression =
-                    when {
-                        assg.target.register != null -> RegisterExpr(assg.target.register!!, assg.target.position)
-                        assg.target.identifier != null -> assg.target.identifier!!
-                        assg.target.arrayindexed != null -> assg.target.arrayindexed!!
-                        assg.target.memoryAddress != null -> DirectMemoryRead(assg.target.memoryAddress!!.addressExpression, assg.value.position)
-                        else -> throw FatalAstException("strange assg")
-                    }
-
-            val expression = BinaryExpression(newTarget, assg.aug_op.substringBeforeLast('='), assg.value, assg.position)
-            expression.linkParents(assg.parent)
-            val convertedAssignment = Assignment(assg.target, null, expression, assg.position)
-            convertedAssignment.linkParents(assg.parent)
-            return super.visit(convertedAssignment)
-        }
-
-        return assg
    }
+
 }
@@ -2,81 +2,113 @@ package prog8.ast.processing

 import prog8.ast.IFunctionCall
 import prog8.ast.INameScope
+import prog8.ast.Node
 import prog8.ast.Program
-import prog8.ast.base.DataType
-import prog8.ast.base.ErrorReporter
-import prog8.ast.base.FatalAstException
+import prog8.ast.base.*
 import prog8.ast.expressions.*
 import prog8.ast.statements.*
 import prog8.functions.BuiltinFunctions


-internal class TypecastsAdder(private val program: Program,
-                              private val errors: ErrorReporter): IAstModifyingVisitor {
-    // Make sure any value assignments get the proper type casts if needed to cast them into the target variable's type.
-    // (this includes function call arguments)
+class TypecastsAdder(val program: Program, val errors: ErrorReporter) : AstWalker() {
+    /*
+     * Make sure any value assignments get the proper type casts if needed to cast them into the target variable's type.
+     * (this includes function call arguments)
+     */

-    override fun visit(expr: BinaryExpression): Expression {
-        val expr2 = super.visit(expr)
-        if(expr2 !is BinaryExpression)
-            return expr2
-        val leftDt = expr2.left.inferType(program)
-        val rightDt = expr2.right.inferType(program)
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
+        val declValue = decl.value
+        if(decl.type==VarDeclType.VAR && declValue!=null && decl.struct==null) {
+            val valueDt = declValue.inferType(program)
+            if(!valueDt.istype(decl.datatype)) {
+                return listOf(IAstModification.ReplaceNode(
+                        declValue,
+                        TypecastExpression(declValue, decl.datatype, true, declValue.position),
+                        decl
+                ))
+            }
+        }
+        return noModifications
+    }
+
+    override fun after(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
+        val leftDt = expr.left.inferType(program)
+        val rightDt = expr.right.inferType(program)
        if(leftDt.isKnown && rightDt.isKnown && leftDt!=rightDt) {
            // determine common datatype and add typecast as required to make left and right equal types
-            val (commonDt, toFix) = BinaryExpression.commonDatatype(leftDt.typeOrElse(DataType.STRUCT), rightDt.typeOrElse(DataType.STRUCT), expr2.left, expr2.right)
+            val (commonDt, toFix) = BinaryExpression.commonDatatype(leftDt.typeOrElse(DataType.STRUCT), rightDt.typeOrElse(DataType.STRUCT), expr.left, expr.right)
            if(toFix!=null) {
-                when {
-                    toFix===expr2.left -> {
-                        expr2.left = TypecastExpression(expr2.left, commonDt, true, expr2.left.position)
-                        expr2.left.linkParents(expr2)
-                    }
-                    toFix===expr2.right -> {
-                        expr2.right = TypecastExpression(expr2.right, commonDt, true, expr2.right.position)
-                        expr2.right.linkParents(expr2)
-                    }
+                return when {
+                    toFix===expr.left -> listOf(IAstModification.ReplaceNode(
+                            expr.left, TypecastExpression(expr.left, commonDt, true, expr.left.position), expr))
+                    toFix===expr.right -> listOf(IAstModification.ReplaceNode(
+                            expr.right, TypecastExpression(expr.right, commonDt, true, expr.right.position), expr))
                    else -> throw FatalAstException("confused binary expression side")
                }
            }
        }
-        return expr2
+        return noModifications
    }

-    override fun visit(assignment: Assignment): Statement {
-        val assg = super.visit(assignment)
-        if(assg !is Assignment)
-            return assg
-
+    override fun after(assignment: Assignment, parent: Node): Iterable<IAstModification> {
        // see if a typecast is needed to convert the value's type into the proper target type
-        val valueItype = assg.value.inferType(program)
-        val targetItype = assg.target.inferType(program, assg)
-
+        val valueItype = assignment.value.inferType(program)
+        val targetItype = assignment.target.inferType(program, assignment)
        if(targetItype.isKnown && valueItype.isKnown) {
            val targettype = targetItype.typeOrElse(DataType.STRUCT)
            val valuetype = valueItype.typeOrElse(DataType.STRUCT)
            if (valuetype != targettype) {
                if (valuetype isAssignableTo targettype) {
-                    assg.value = TypecastExpression(assg.value, targettype, true, assg.value.position)
-                    assg.value.linkParents(assg)
+                    return listOf(IAstModification.ReplaceNode(
+                            assignment.value,
+                            TypecastExpression(assignment.value, targettype, true, assignment.value.position),
+                            assignment))
+                } else {
+                    fun castLiteral(cvalue: NumericLiteralValue): List<IAstModification.ReplaceNode> {
+                        val cast = cvalue.cast(targettype)
+                        return if(cast.isValid)
+                            listOf(IAstModification.ReplaceNode(cvalue, cast.valueOrZero(), cvalue.parent))
+                        else
+                            emptyList()
+                    }
+                    val cvalue = assignment.value.constValue(program)
+                    if(cvalue!=null) {
+                        val number = cvalue.number.toDouble()
+                        // more complex comparisons if the type is different, but the constant value is compatible
+                        if (valuetype == DataType.BYTE && targettype == DataType.UBYTE) {
+                            if(number>0)
+                                return castLiteral(cvalue)
+                        } else if (valuetype == DataType.WORD && targettype == DataType.UWORD) {
+                            if(number>0)
+                                return castLiteral(cvalue)
+                        } else if (valuetype == DataType.UBYTE && targettype == DataType.BYTE) {
+                            if(number<0x80)
+                                return castLiteral(cvalue)
+                        } else if (valuetype == DataType.UWORD && targettype == DataType.WORD) {
+                            if(number<0x8000)
+                                return castLiteral(cvalue)
+                        }
+                    }
                }
-                // if they're not assignable, we'll get a proper error later from the AstChecker
            }
        }
-        return assg
+        return noModifications
    }

-    override fun visit(functionCallStatement: FunctionCallStatement): Statement {
-        checkFunctionCallArguments(functionCallStatement, functionCallStatement.definingScope())
-        return super.visit(functionCallStatement)
+    override fun after(functionCallStatement: FunctionCallStatement, parent: Node): Iterable<IAstModification> {
+        return afterFunctionCallArgs(functionCallStatement, functionCallStatement.definingScope())
    }

-    override fun visit(functionCall: FunctionCall): Expression {
-        checkFunctionCallArguments(functionCall, functionCall.definingScope())
-        return super.visit(functionCall)
+    override fun after(functionCall: FunctionCall, parent: Node): Iterable<IAstModification> {
+        return afterFunctionCallArgs(functionCall, functionCall.definingScope())
    }

-    private fun checkFunctionCallArguments(call: IFunctionCall, scope: INameScope) {
+    private fun afterFunctionCallArgs(call: IFunctionCall, scope: INameScope): Iterable<IAstModification> {
        // see if a typecast is needed to convert the arguments into the required parameter's type
+        val modifications = mutableListOf<IAstModification>()
+
        when(val sub = call.target.targetStatement(scope)) {
            is Subroutine -> {
                for(arg in sub.parameters.zip(call.args.withIndex())) {
@@ -86,114 +118,105 @@ internal class TypecastsAdder(private val program: Program,
                        val requiredType = arg.first.type
                        if (requiredType != argtype) {
                            if (argtype isAssignableTo requiredType) {
-                                val typecasted = TypecastExpression(arg.second.value, requiredType, true, arg.second.value.position)
-                                typecasted.linkParents(arg.second.value.parent)
-                                call.args[arg.second.index] = typecasted
+                                modifications += IAstModification.ReplaceNode(
+                                        call.args[arg.second.index],
+                                        TypecastExpression(arg.second.value, requiredType, true, arg.second.value.position),
+                                        call as Node)
+                            } else if(requiredType == DataType.UWORD && argtype in PassByReferenceDatatypes) {
+                                // we allow STR/ARRAY values in place of UWORD parameters. Take their address instead.
+                                modifications += IAstModification.ReplaceNode(
+                                        call.args[arg.second.index],
+                                        AddressOf(arg.second.value as IdentifierReference, arg.second.value.position),
+                                        call as Node)
+                            } else if(arg.second.value is NumericLiteralValue) {
+                                val cast = (arg.second.value as NumericLiteralValue).cast(requiredType)
+                                if(cast.isValid)
+                                    modifications += IAstModification.ReplaceNode(
+                                            call.args[arg.second.index],
+                                            cast.valueOrZero(),
+                                            call as Node)
                            }
-                            // if they're not assignable, we'll get a proper error later from the AstChecker
                        }
                    }
                }
            }
            is BuiltinFunctionStatementPlaceholder -> {
                val func = BuiltinFunctions.getValue(sub.name)
-                if(func.pure) {
-                    // non-pure functions don't get automatic typecasts because sometimes they act directly on their parameters
-                    for (arg in func.parameters.zip(call.args.withIndex())) {
-                        val argItype = arg.second.value.inferType(program)
-                        if (argItype.isKnown) {
-                            val argtype = argItype.typeOrElse(DataType.STRUCT)
-                            if (arg.first.possibleDatatypes.any { argtype == it })
-                                continue
-                            for (possibleType in arg.first.possibleDatatypes) {
-                                if (argtype isAssignableTo possibleType) {
-                                    val typecasted = TypecastExpression(arg.second.value, possibleType, true, arg.second.value.position)
-                                    typecasted.linkParents(arg.second.value.parent)
-                                    call.args[arg.second.index] = typecasted
-                                    break
-                                }
+                for (arg in func.parameters.zip(call.args.withIndex())) {
+                    val argItype = arg.second.value.inferType(program)
+                    if (argItype.isKnown) {
+                        val argtype = argItype.typeOrElse(DataType.STRUCT)
+                        if (arg.first.possibleDatatypes.any { argtype == it })
+                            continue
+                        for (possibleType in arg.first.possibleDatatypes) {
+                            if (argtype isAssignableTo possibleType) {
+                                modifications += IAstModification.ReplaceNode(
+                                        call.args[arg.second.index],
+                                        TypecastExpression(arg.second.value, possibleType, true, arg.second.value.position),
+                                        call as Node)
+                                break
                            }
                        }
                    }
                }
            }
-            null -> {}
-            else -> throw FatalAstException("call to something weird $sub   ${call.target}")
+            else -> { }
        }
+
+        return modifications
    }

-    override fun visit(typecast: TypecastExpression): Expression {
+    override fun after(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> {
        // warn about any implicit type casts to Float, because that may not be intended
        if(typecast.implicit && typecast.type in setOf(DataType.FLOAT, DataType.ARRAY_F)) {
-            errors.warn("byte or word value implicitly converted to float. Suggestion: use explicit cast as float, a float number, or revert to integer arithmetic", typecast.position)
+            errors.warn("integer implicitly converted to float. Suggestion: use float literals, add an explicit cast, or revert to integer arithmetic", typecast.position)
        }
-        return super.visit(typecast)
+        return noModifications
    }

-    override fun visit(memread: DirectMemoryRead): Expression {
+    override fun after(memread: DirectMemoryRead, parent: Node): Iterable<IAstModification> {
        // make sure the memory address is an uword
        val dt = memread.addressExpression.inferType(program)
        if(dt.isKnown && dt.typeOrElse(DataType.UWORD)!=DataType.UWORD) {
-            val literaladdr = memread.addressExpression as? NumericLiteralValue
-            if(literaladdr!=null) {
-                memread.addressExpression = literaladdr.cast(DataType.UWORD)
-            } else {
-                memread.addressExpression = TypecastExpression(memread.addressExpression, DataType.UWORD, true, memread.addressExpression.position)
-                memread.addressExpression.parent = memread
-            }
+            val typecast = (memread.addressExpression as? NumericLiteralValue)?.cast(DataType.UWORD)?.valueOrZero()
+                    ?: TypecastExpression(memread.addressExpression, DataType.UWORD, true, memread.addressExpression.position)
+            return listOf(IAstModification.ReplaceNode(memread.addressExpression, typecast, memread))
        }
-        return super.visit(memread)
+        return noModifications
    }

-    override fun visit(memwrite: DirectMemoryWrite) {
+    override fun after(memwrite: DirectMemoryWrite, parent: Node): Iterable<IAstModification> {
+        // make sure the memory address is an uword
        val dt = memwrite.addressExpression.inferType(program)
        if(dt.isKnown && dt.typeOrElse(DataType.UWORD)!=DataType.UWORD) {
-            val literaladdr = memwrite.addressExpression as? NumericLiteralValue
-            if(literaladdr!=null) {
-                memwrite.addressExpression = literaladdr.cast(DataType.UWORD)
-            } else {
-                memwrite.addressExpression = TypecastExpression(memwrite.addressExpression, DataType.UWORD, true, memwrite.addressExpression.position)
-                memwrite.addressExpression.parent = memwrite
-            }
+            val typecast = (memwrite.addressExpression as? NumericLiteralValue)?.cast(DataType.UWORD)?.valueOrZero()
+                    ?: TypecastExpression(memwrite.addressExpression, DataType.UWORD, true, memwrite.addressExpression.position)
+            return listOf(IAstModification.ReplaceNode(memwrite.addressExpression, typecast, memwrite))
        }
-        super.visit(memwrite)
+        return noModifications
    }

-    override fun visit(structLv: StructLiteralValue): Expression {
-        val litval = super.visit(structLv)
-        if(litval !is StructLiteralValue)
-            return litval
-
-        val decl = litval.parent as? VarDecl
-        if(decl != null) {
-            val struct = decl.struct
-            if(struct != null) {
-                addTypecastsIfNeeded(litval, struct)
-            }
-        } else {
-            val assign = litval.parent as? Assignment
-            if (assign != null) {
-                val decl2 = assign.target.identifier?.targetVarDecl(program.namespace)
-                if(decl2 != null) {
-                    val struct = decl2.struct
-                    if(struct != null) {
-                        addTypecastsIfNeeded(litval, struct)
-                    }
+    override fun after(returnStmt: Return, parent: Node): Iterable<IAstModification> {
+        // add a typecast to the return type if it doesn't match the subroutine's signature
+        val returnValue = returnStmt.value
+        if(returnValue!=null) {
+            val subroutine = returnStmt.definingSubroutine()!!
+            if(subroutine.returntypes.size==1) {
+                val subReturnType = subroutine.returntypes.first()
+                if (returnValue.inferType(program).istype(subReturnType))
+                    return noModifications
+                if (returnValue is NumericLiteralValue) {
+                    val cast = returnValue.cast(subroutine.returntypes.single())
+                    if(cast.isValid)
+                        returnStmt.value = cast.valueOrZero()
+                } else {
+                    return listOf(IAstModification.ReplaceNode(
+                            returnValue,
+                            TypecastExpression(returnValue, subReturnType, true, returnValue.position),
+                            returnStmt))
                }
            }
        }
-
-        return litval
-    }
-
-    private fun addTypecastsIfNeeded(structLv: StructLiteralValue, struct: StructDecl) {
-        structLv.values = struct.statements.zip(structLv.values).map {
-            val memberDt = (it.first as VarDecl).datatype
-            val valueDt = it.second.inferType(program)
-            if (valueDt.typeOrElse(memberDt) != memberDt)
-                TypecastExpression(it.second, memberDt, true, it.second.position)
-            else
-                it.second
-        }
+        return noModifications
    }
 }
@@ -1,156 +0,0 @@
-package prog8.ast.processing
-
-import prog8.ast.INameScope
-import prog8.ast.Module
-import prog8.ast.Node
-import prog8.ast.Program
-import prog8.ast.base.*
-import prog8.ast.expressions.*
-import prog8.ast.statements.*
-import prog8.compiler.CompilerException
-import prog8.functions.BuiltinFunctions
-import prog8.functions.FSignature
-
-
-internal class VarInitValueAndAddressOfCreator(private val program: Program): IAstModifyingVisitor {
-    // For VarDecls that declare an initialization value:
-    // Replace the vardecl with an assignment (to set the initial value),
-    // and add a new vardecl with the default constant value of that type (usually zero) to the scope.
-    // This makes sure the variables get reset to the intended value on a next run of the program.
-    // Variable decls without a value don't get this treatment, which means they retain the last
-    // value they had when restarting the program.
-    // This is done in a separate step because it interferes with the namespace lookup of symbols
-    // in other ast processors.
-
-    // Also takes care to insert AddressOf (&) expression where required (string params to a UWORD function param etc).
-
-    private val vardeclsToAdd = mutableMapOf<INameScope, MutableList<VarDecl>>()
-
-    override fun visit(module: Module) {
-        vardeclsToAdd.clear()
-        super.visit(module)
-        // add any new vardecls to the various scopes
-        for((where, decls) in vardeclsToAdd) {
-            where.statements.addAll(0, decls)
-            decls.forEach { it.linkParents(where as Node) }
-        }
-    }
-
-    override fun visit(decl: VarDecl): Statement {
-        super.visit(decl)
-
-        if(decl.isArray && decl.value==null) {
-            // array datatype without initialization value, add list of zeros
-            val arraysize = decl.arraysize!!.size()!!
-            val array = ArrayLiteralValue(InferredTypes.InferredType.known(decl.datatype),
-                    Array(arraysize) { NumericLiteralValue.optimalInteger(0, decl.position) },
-                    decl.position)
-            decl.value = array
-        }
-
-        if(decl.type!= VarDeclType.VAR || decl.value==null)
-            return decl
-
-        if(decl.datatype in NumericDatatypes) {
-            val scope = decl.definingScope()
-            addVarDecl(scope, decl.asDefaultValueDecl(null))
-            val declvalue = decl.value!!
-            val value =
-                    if(declvalue is NumericLiteralValue)
-                        declvalue.cast(decl.datatype)
-                    else
-                        declvalue
-            val identifierName = listOf(decl.name)    // this was: (scoped name) decl.scopedname.split(".")
-            return VariableInitializationAssignment(
-                    AssignTarget(null, IdentifierReference(identifierName, decl.position), null, null, decl.position),
-                    null,
-                    value,
-                    decl.position
-            )
-        }
-
-        return decl
-    }
-
-    override fun visit(functionCall: FunctionCall): Expression {
-        var parentStatement: Node = functionCall
-        while(parentStatement !is Statement)
-            parentStatement = parentStatement.parent
-        val targetStatement = functionCall.target.targetSubroutine(program.namespace)
-        if(targetStatement!=null) {
-            addAddressOfExprIfNeeded(targetStatement, functionCall.args, parentStatement)
-        } else {
-            val builtinFunc = BuiltinFunctions[functionCall.target.nameInSource.joinToString (".")]
-            if(builtinFunc!=null)
-                addAddressOfExprIfNeededForBuiltinFuncs(builtinFunc, functionCall.args, parentStatement)
-        }
-        return functionCall
-    }
-
-    override fun visit(functionCallStatement: FunctionCallStatement): Statement {
-        val targetStatement = functionCallStatement.target.targetSubroutine(program.namespace)
-        if(targetStatement!=null) {
-            addAddressOfExprIfNeeded(targetStatement, functionCallStatement.args, functionCallStatement)
-        } else {
-            val builtinFunc = BuiltinFunctions[functionCallStatement.target.nameInSource.joinToString (".")]
-            if(builtinFunc!=null)
-                addAddressOfExprIfNeededForBuiltinFuncs(builtinFunc, functionCallStatement.args, functionCallStatement)
-        }
-        return functionCallStatement
-    }
-
-    private fun addAddressOfExprIfNeeded(subroutine: Subroutine, arglist: MutableList<Expression>, parent: Statement) {
-        // functions that accept UWORD and are given an array type, or string, will receive the AddressOf (memory location) of that value instead.
-        for(argparam in subroutine.parameters.withIndex().zip(arglist)) {
-            if(argparam.first.value.type==DataType.UWORD || argparam.first.value.type == DataType.STR) {
-                if(argparam.second is AddressOf)
-                    continue
-                val idref = argparam.second as? IdentifierReference
-                val strvalue = argparam.second as? StringLiteralValue
-                if(idref!=null) {
-                    val variable = idref.targetVarDecl(program.namespace)
-                    if(variable!=null && variable.datatype in IterableDatatypes) {
-                        val pointerExpr = AddressOf(idref, idref.position)
-                        pointerExpr.linkParents(arglist[argparam.first.index].parent)
-                        arglist[argparam.first.index] = pointerExpr
-                    }
-                }
-                else if(strvalue!=null) {
-                    // add a vardecl so that the autovar can be resolved in later lookups
-                    val variable = VarDecl.createAuto(strvalue)
-                    addVarDecl(strvalue.definingScope(), variable)
-                    // replace the argument with &autovar
-                    val autoHeapvarRef = IdentifierReference(listOf(variable.name), strvalue.position)
-                    val pointerExpr = AddressOf(autoHeapvarRef, strvalue.position)
-                    pointerExpr.linkParents(arglist[argparam.first.index].parent)
-                    arglist[argparam.first.index] = pointerExpr
-                }
-            }
-        }
-    }
-
-    private fun addAddressOfExprIfNeededForBuiltinFuncs(signature: FSignature, args: MutableList<Expression>, parent: Statement) {
-        // val paramTypesForAddressOf = PassByReferenceDatatypes + DataType.UWORD
-        for(arg in args.withIndex().zip(signature.parameters)) {
-            val argvalue = arg.first.value
-            val argDt = argvalue.inferType(program)
-            if(argDt.typeOrElse(DataType.UBYTE) in PassByReferenceDatatypes && DataType.UWORD in arg.second.possibleDatatypes) {
-                if(argvalue !is IdentifierReference)
-                    throw CompilerException("pass-by-reference parameter isn't an identifier? $argvalue")
-                val addrOf = AddressOf(argvalue, argvalue.position)
-                args[arg.first.index] = addrOf
-                addrOf.linkParents(parent)
-            }
-        }
-    }
-
-
-    private fun addVarDecl(scope: INameScope, variable: VarDecl) {
-        if(scope !in vardeclsToAdd)
-            vardeclsToAdd[scope] = mutableListOf()
-        val declList = vardeclsToAdd.getValue(scope)
-        if(declList.all{it.name!=variable.name})
-            declList.add(variable)
-    }
-
-}
@@ -0,0 +1,44 @@
+package prog8.ast.processing
+
+import prog8.ast.INameScope
+import prog8.ast.Node
+import prog8.ast.expressions.NumericLiteralValue
+import prog8.ast.expressions.TypecastExpression
+import prog8.ast.statements.AnonymousScope
+import prog8.ast.statements.NopStatement
+
+
+internal class VariousCleanups: AstWalker() {
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun before(nopStatement: NopStatement, parent: Node): Iterable<IAstModification> {
+        return listOf(IAstModification.Remove(nopStatement, parent))
+    }
+
+    override fun before(scope: AnonymousScope, parent: Node): Iterable<IAstModification> {
+        return if(parent is INameScope)
+            listOf(ScopeFlatten(scope, parent as INameScope))
+        else
+            noModifications
+    }
+
+    class ScopeFlatten(val scope: AnonymousScope, val into: INameScope) : IAstModification {
+        override fun perform() {
+            val idx = into.statements.indexOf(scope)
+            if(idx>=0) {
+                into.statements.addAll(idx+1, scope.statements)
+                into.statements.remove(scope)
+            }
+        }
+    }
+
+    override fun before(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> {
+        if(typecast.expression is NumericLiteralValue) {
+            val value = (typecast.expression as NumericLiteralValue).cast(typecast.type)
+            if(value.isValid)
+                return listOf(IAstModification.ReplaceNode(typecast, value.valueOrZero(), parent))
+        }
+
+        return noModifications
+    }
+}
@@ -0,0 +1,61 @@
+package prog8.ast.processing
+
+import prog8.ast.IFunctionCall
+import prog8.ast.INameScope
+import prog8.ast.Program
+import prog8.ast.base.DataType
+import prog8.ast.expressions.FunctionCall
+import prog8.ast.statements.BuiltinFunctionStatementPlaceholder
+import prog8.ast.statements.FunctionCallStatement
+import prog8.ast.statements.Subroutine
+import prog8.compiler.CompilerException
+import prog8.functions.BuiltinFunctions
+
+class VerifyFunctionArgTypes(val program: Program) : IAstVisitor {
+
+    override fun visit(functionCall: FunctionCall) {
+        val error = checkTypes(functionCall as IFunctionCall, functionCall.definingScope(), program)
+        if(error!=null)
+            throw CompilerException(error)
+    }
+
+    override fun visit(functionCallStatement: FunctionCallStatement) {
+        val error = checkTypes(functionCallStatement as IFunctionCall, functionCallStatement.definingScope(), program)
+        if (error!=null)
+            throw CompilerException(error)
+    }
+
+    companion object {
+        fun checkTypes(call: IFunctionCall, scope: INameScope, program: Program): String? {
+            val argtypes = call.args.map { it.inferType(program).typeOrElse(DataType.STRUCT) }
+            val target = call.target.targetStatement(scope)
+            if (target is Subroutine) {
+                // asmsub types are not checked specifically at this time
+                if(call.args.size != target.parameters.size)
+                    return "invalid number of arguments"
+                val paramtypes = target.parameters.map { it.type }
+                val mismatch = argtypes.zip(paramtypes).indexOfFirst { it.first != it.second}
+                if(mismatch>=0) {
+                    val actual = argtypes[mismatch].toString()
+                    val expected = paramtypes[mismatch].toString()
+                    return "argument ${mismatch + 1} type mismatch, was: $actual expected: $expected"
+                }
+            }
+            else if (target is BuiltinFunctionStatementPlaceholder) {
+                val func = BuiltinFunctions.getValue(target.name)
+                if(call.args.size != func.parameters.size)
+                    return "invalid number of arguments"
+                val paramtypes = func.parameters.map { it.possibleDatatypes }
+                for (x in argtypes.zip(paramtypes).withIndex()) {
+                    if (x.value.first !in x.value.second) {
+                        val actual = x.value.first.toString()
+                        val expected = x.value.second.toString()
+                        return "argument ${x.index + 1} type mismatch, was: $actual expected: $expected"
+                    }
+                }
+            }
+
+            return null
+        }
+    }
+}
@@ -3,13 +3,14 @@ package prog8.ast.statements
 import prog8.ast.*
 import prog8.ast.base.*
 import prog8.ast.expressions.*
-import prog8.ast.processing.IAstModifyingVisitor
+import prog8.ast.processing.AstWalker
 import prog8.ast.processing.IAstVisitor


 sealed class Statement : Node {
-    abstract fun accept(visitor: IAstModifyingVisitor) : Statement
    abstract fun accept(visitor: IAstVisitor)
+    abstract fun accept(visitor: AstWalker, parent: Node)
+
    fun makeScopedName(name: String): String {
        // easy way out is to always return the full scoped name.
        // it would be nicer to find only the minimal prefixed scoped name, but that's too much hassle for now.
@@ -28,8 +29,6 @@ sealed class Statement : Node {
        return scope.joinToString(".")
    }

-    abstract val expensiveToInline: Boolean
-
    fun definingBlock(): Block {
        if(this is Block)
            return this
@@ -37,13 +36,16 @@ sealed class Statement : Node {
    }
 }

+
 class BuiltinFunctionStatementPlaceholder(val name: String, override val position: Position) : Statement() {
    override var parent: Node = ParentSentinel
    override fun linkParents(parent: Node) {}
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
    override fun definingScope(): INameScope = BuiltinFunctionScopePlaceholder
-    override val expensiveToInline = false
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        replacement.parent = this
+    }
 }

 data class RegisterOrStatusflag(val registerOrPair: RegisterOrPair?, val statusflag: Statusflag?, val stack: Boolean)
@@ -54,16 +56,21 @@ class Block(override val name: String,
            val isInLibrary: Boolean,
            override val position: Position) : Statement(), INameScope {
    override lateinit var parent: Node
-    override val expensiveToInline
-        get() = statements.any { it.expensiveToInline }

    override fun linkParents(parent: Node) {
        this.parent = parent
        statements.forEach {it.linkParents(this)}
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Statement)
+        val idx = statements.indexOfFirst { it ===node }
+        statements[idx] = replacement
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
        return "Block(name=$name, address=$address, ${statements.size} statements)"
@@ -74,15 +81,15 @@ class Block(override val name: String,

 data class Directive(val directive: String, val args: List<DirectiveArg>, override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = false

    override fun linkParents(parent: Node) {
        this.parent = parent
        args.forEach{it.linkParents(this)}
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) = throw FatalAstException("can't replace here")
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

 data class DirectiveArg(val str: String?, val name: String?, val int: Int?, override val position: Position) : Node {
@@ -91,18 +98,19 @@ data class DirectiveArg(val str: String?, val name: String?, val int: Int?, over
    override fun linkParents(parent: Node) {
        this.parent = parent
    }
+    override fun replaceChildNode(node: Node, replacement: Node) = throw FatalAstException("can't replace here")
 }

 data class Label(val name: String, override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = false

    override fun linkParents(parent: Node) {
        this.parent = parent
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) = throw FatalAstException("can't replace here")
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
        return "Label(name=$name, pos=$position)"
@@ -111,52 +119,36 @@ data class Label(val name: String, override val position: Position) : Statement(

 open class Return(var value: Expression?, override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = value!=null && value !is NumericLiteralValue

    override fun linkParents(parent: Node) {
        this.parent = parent
        value?.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression)
+        value = replacement
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
        return "Return($value, pos=$position)"
    }
 }

-class ReturnFromIrq(override val position: Position) : Return(null, position) {
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
-    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
-
-    override fun toString(): String {
-        return "ReturnFromIrq(pos=$position)"
-    }
-}
-
-class Continue(override val position: Position) : Statement() {
-    override lateinit var parent: Node
-    override val expensiveToInline = false
-
-    override fun linkParents(parent: Node) {
-        this.parent=parent
-    }
-
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
-    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
-}
-
 class Break(override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = false

    override fun linkParents(parent: Node) {
        this.parent=parent
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) = throw FatalAstException("can't replace here")
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }


@@ -167,7 +159,8 @@ enum class ZeropageWish {
    NOT_IN_ZEROPAGE
 }

-class VarDecl(val type: VarDeclType,
+
+open class VarDecl(val type: VarDeclType,
              private val declaredDatatype: DataType,
              val zeropage: ZeropageWish,
              var arraysize: ArrayIndex?,
@@ -183,9 +176,6 @@ class VarDecl(val type: VarDeclType,
    var structHasBeenFlattened = false      // set later
        private set

-    override val expensiveToInline
-            get() = value!=null && value !is NumericLiteralValue
-
    // prefix for literal values that are turned into a variable on the heap

    companion object {
@@ -204,6 +194,15 @@ class VarDecl(val type: VarDeclType,
            return VarDecl(VarDeclType.VAR, declaredType, ZeropageWish.NOT_IN_ZEROPAGE, arraysize, autoVarName, null, array,
                    isArray = true, autogeneratedDontRemove = true, position = array.position)
        }
+
+        fun defaultZero(dt: DataType, position: Position) = when(dt) {
+            DataType.UBYTE -> NumericLiteralValue(DataType.UBYTE, 0,  position)
+            DataType.BYTE -> NumericLiteralValue(DataType.BYTE, 0,  position)
+            DataType.UWORD -> NumericLiteralValue(DataType.UWORD, 0, position)
+            DataType.WORD -> NumericLiteralValue(DataType.WORD, 0, position)
+            DataType.FLOAT -> NumericLiteralValue(DataType.FLOAT, 0.0, position)
+            else -> throw FatalAstException("can only determine default zero value for a numeric type")
+        }
    }

    val datatypeErrors = mutableListOf<SyntaxError>()       // don't crash at init time, report them in the AstChecker
@@ -232,34 +231,25 @@ class VarDecl(val type: VarDeclType,
        }
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
-    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression && node===value)
+        value = replacement
+        replacement.parent = this
+    }

-    val scopedname: String by lazy { makeScopedName(name) }
+    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
        return "VarDecl(name=$name, vartype=$type, datatype=$datatype, struct=$structName, value=$value, pos=$position)"
    }

-    fun asDefaultValueDecl(parent: Node?): VarDecl {
-        val constValue = when(declaredDatatype) {
-            DataType.UBYTE -> NumericLiteralValue(DataType.UBYTE, 0,  position)
-            DataType.BYTE -> NumericLiteralValue(DataType.BYTE, 0,  position)
-            DataType.UWORD -> NumericLiteralValue(DataType.UWORD, 0, position)
-            DataType.WORD -> NumericLiteralValue(DataType.WORD, 0, position)
-            DataType.FLOAT -> NumericLiteralValue(DataType.FLOAT, 0.0, position)
-            else -> throw FatalAstException("can only set a default value for a numeric type")
-        }
-        val decl = VarDecl(type, declaredDatatype, zeropage, arraysize, name, structName, constValue, isArray, false, position)
-        if(parent!=null)
-            decl.linkParents(parent)
-        return decl
-    }
+    fun zeroElementValue() = defaultZero(declaredDatatype, position)

    fun flattenStructMembers(): MutableList<Statement> {
        val result = struct!!.statements.withIndex().map {
            val member = it.value as VarDecl
-            val initvalue = if(value!=null) (value as StructLiteralValue).values[it.index] else null
+            val initvalue = if(value!=null) (value as ArrayLiteralValue).value[it.index] else null
            VarDecl(
                    VarDeclType.VAR,
                    member.datatype,
@@ -271,13 +261,18 @@ class VarDecl(val type: VarDeclType,
                    member.isArray,
                    true,
                    member.position
-            ) as Statement
-        }.toMutableList()
+            )
+        }.toMutableList<Statement>()
        structHasBeenFlattened = true
        return result
    }
 }

+// a vardecl used only for subroutine parameters
+class ParameterVarDecl(name: String, declaredDatatype: DataType, position: Position)
+    : VarDecl(VarDeclType.VAR, declaredDatatype, ZeropageWish.DONTCARE, null, name, null, null, false, true, position)
+
+
 class ArrayIndex(var index: Expression, override val position: Position) : Node {
    override lateinit var parent: Node

@@ -286,31 +281,30 @@ class ArrayIndex(var index: Expression, override val position: Position) : Node
        index.linkParents(this)
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression && node===index)
+        index = replacement
+        replacement.parent = this
+    }
+
    companion object {
        fun forArray(v: ArrayLiteralValue): ArrayIndex {
            return ArrayIndex(NumericLiteralValue.optimalNumeric(v.value.size, v.position), v.position)
        }
    }

-    fun accept(visitor: IAstModifyingVisitor) {
-        index = index.accept(visitor)
-    }
-
-    fun accept(visitor: IAstVisitor) {
-        index.accept(visitor)
-    }
+    fun accept(visitor: IAstVisitor) = index.accept(visitor)
+    fun accept(visitor: AstWalker, parent: Node) = index.accept(visitor, this)

    override fun toString(): String {
        return("ArrayIndex($index, pos=$position)")
    }

-    fun size() = (index as? NumericLiteralValue)?.number?.toInt()
+    fun constIndex() = (index as? NumericLiteralValue)?.number?.toInt()
 }

-open class Assignment(var target: AssignTarget, val aug_op : String?, var value: Expression, override val position: Position) : Statement() {
+open class Assignment(var target: AssignTarget, var value: Expression, override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline
-            get() = value !is NumericLiteralValue

    override fun linkParents(parent: Node) {
        this.parent = parent
@@ -318,21 +312,71 @@ open class Assignment(var target: AssignTarget, val aug_op : String?, var value:
        value.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===target -> target = replacement as AssignTarget
+            node===value -> value = replacement as Expression
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
-        return("Assignment(augop: $aug_op, target: $target, value: $value, pos=$position)")
+        return("Assignment(target: $target, value: $value, pos=$position)")
    }
+
+    /**
+     * Is the assigment value an expression that references the assignment target itself?
+     * The expression can be a BinaryExpression, PrefixExpression or TypecastExpression (possibly with one sub-cast).
+     */
+    val isAugmentable: Boolean
+        get() {
+            val binExpr = value as? BinaryExpression
+            if(binExpr!=null) {
+                if(binExpr.left isSameAs target)
+                    return true  // A = A <operator> Something
+
+                if(binExpr.operator in associativeOperators) {
+                    if (binExpr.left !is BinaryExpression && binExpr.right isSameAs target)
+                        return true  // A = v <associative-operator> A
+
+                    val leftBinExpr = binExpr.left as? BinaryExpression
+                    if(leftBinExpr?.operator == binExpr.operator) {
+                        // one of these?
+                        // A = (A <associative-operator> x) <same-operator> y
+                        // A = (x <associative-operator> A) <same-operator> y
+                        // A = (x <associative-operator> y) <same-operator> A
+                        return leftBinExpr.left isSameAs target || leftBinExpr.right isSameAs target || binExpr.right isSameAs target
+                    }
+                    val rightBinExpr = binExpr.right as? BinaryExpression
+                    if(rightBinExpr?.operator == binExpr.operator) {
+                        // one of these?
+                        // A = y <associative-operator> (A <same-operator> x)
+                        // A = y <associative-operator> (x <same-operator> y)
+                        // A = A <associative-operator> (x <same-operator> y)
+                        return rightBinExpr.left isSameAs target || rightBinExpr.right isSameAs target || binExpr.left isSameAs target
+                    }
+                }
+            }
+
+            val prefixExpr = value as? PrefixExpression
+            if(prefixExpr!=null)
+                return prefixExpr.expression isSameAs target
+
+            val castExpr = value as? TypecastExpression
+            if(castExpr!=null) {
+                val subCast = castExpr.expression as? TypecastExpression
+                return if(subCast!=null) subCast.expression isSameAs target else castExpr.expression isSameAs target
+            }
+
+            return false
+        }
 }

-// This is a special class so the compiler can see if the assignments are for initializing the vars in the scope,
-// or just a regular assignment. It may optimize the initialization step from this.
-class VariableInitializationAssignment(target: AssignTarget, aug_op: String?, value: Expression, position: Position)
-    : Assignment(target, aug_op, value, position)
-
-data class AssignTarget(val register: Register?,
-                        var identifier: IdentifierReference?,
+data class AssignTarget(var identifier: IdentifierReference?,
                        var arrayindexed: ArrayIndexedExpression?,
                        val memoryAddress: DirectMemoryWrite?,
                        override val position: Position) : Node {
@@ -345,25 +389,30 @@ data class AssignTarget(val register: Register?,
        memoryAddress?.linkParents(this)
    }

-    fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===identifier -> identifier = replacement as IdentifierReference
+            node===arrayindexed -> arrayindexed = replacement as ArrayIndexedExpression
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    companion object {
        fun fromExpr(expr: Expression): AssignTarget {
            return when (expr) {
-                is RegisterExpr -> AssignTarget(expr.register, null, null, null, expr.position)
-                is IdentifierReference -> AssignTarget(null, expr, null, null, expr.position)
-                is ArrayIndexedExpression -> AssignTarget(null, null, expr, null, expr.position)
-                is DirectMemoryRead -> AssignTarget(null, null, null, DirectMemoryWrite(expr.addressExpression, expr.position), expr.position)
+                is IdentifierReference -> AssignTarget(expr, null, null, expr.position)
+                is ArrayIndexedExpression -> AssignTarget(null, expr, null, expr.position)
+                is DirectMemoryRead -> AssignTarget(null, null, DirectMemoryWrite(expr.addressExpression, expr.position), expr.position)
                else -> throw FatalAstException("invalid expression object $expr")
            }
        }
    }

    fun inferType(program: Program, stmt: Statement): InferredTypes.InferredType {
-        if(register!=null)
-            return InferredTypes.knownFor(DataType.UBYTE)
-
        if(identifier!=null) {
            val symbol = program.namespace.lookup(identifier!!.nameInSource, stmt) ?: return InferredTypes.unknown()
            if (symbol is VarDecl) return InferredTypes.knownFor(symbol.datatype)
@@ -379,16 +428,30 @@ data class AssignTarget(val register: Register?,
        return InferredTypes.unknown()
    }

+    fun toExpression(): Expression {
+        return when {
+            identifier!=null -> identifier!!
+            arrayindexed!=null -> arrayindexed!!
+            memoryAddress!=null -> DirectMemoryRead(memoryAddress.addressExpression, memoryAddress.position)
+            else -> throw FatalAstException("invalid assignmenttarget $this")
+        }
+    }
+
    infix fun isSameAs(value: Expression): Boolean {
        return when {
-            this.memoryAddress!=null -> false
-            this.register!=null -> value is RegisterExpr && value.register==register
+            this.memoryAddress!=null -> {
+                // if the target is a memory write, and the value is a memory read, they're the same if the address matches
+                if(value is DirectMemoryRead)
+                    this.memoryAddress.addressExpression isSameAs value.addressExpression
+                else
+                    false
+            }
            this.identifier!=null -> value is IdentifierReference && value.nameInSource==identifier!!.nameInSource
            this.arrayindexed!=null -> value is ArrayIndexedExpression &&
                    value.identifier.nameInSource==arrayindexed!!.identifier.nameInSource &&
-                    value.arrayspec.size()!=null &&
-                    arrayindexed!!.arrayspec.size()!=null &&
-                    value.arrayspec.size()==arrayindexed!!.arrayspec.size()
+                    value.arrayspec.constIndex()!=null &&
+                    arrayindexed!!.arrayspec.constIndex()!=null &&
+                    value.arrayspec.constIndex()==arrayindexed!!.arrayspec.constIndex()
            else -> false
        }
    }
@@ -396,8 +459,6 @@ data class AssignTarget(val register: Register?,
    fun isSameAs(other: AssignTarget, program: Program): Boolean {
        if(this===other)
            return true
-        if(this.register!=null && other.register!=null)
-            return this.register==other.register
        if(this.identifier!=null && other.identifier!=null)
            return this.identifier!!.nameInSource==other.identifier!!.nameInSource
        if(this.memoryAddress!=null && other.memoryAddress!=null) {
@@ -416,8 +477,6 @@ data class AssignTarget(val register: Register?,
    }

    fun isNotMemory(namespace: INameScope): Boolean {
-        if(this.register!=null)
-            return true
        if(this.memoryAddress!=null)
            return false
        if(this.arrayindexed!=null) {
@@ -436,15 +495,20 @@ data class AssignTarget(val register: Register?,

 class PostIncrDecr(var target: AssignTarget, val operator: String, override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = false

    override fun linkParents(parent: Node) {
        this.parent = parent
        target.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is AssignTarget && node===target)
+        target = replacement
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
        return "PostIncrDecr(op: $operator, target: $target, pos=$position)"
@@ -456,15 +520,15 @@ class Jump(val address: Int?,
           val generatedLabel: String?,             // used in code generation scenarios
           override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = false

    override fun linkParents(parent: Node) {
        this.parent = parent
        identifier?.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) = throw FatalAstException("can't replace here")
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
        return "Jump(addr: $address, identifier: $identifier, label: $generatedLabel;  pos=$position)"
@@ -476,8 +540,6 @@ class FunctionCallStatement(override var target: IdentifierReference,
                            val void: Boolean,
                            override val position: Position) : Statement(), IFunctionCall {
    override lateinit var parent: Node
-    override val expensiveToInline
-            get() = args.any { it !is NumericLiteralValue }

    override fun linkParents(parent: Node) {
        this.parent = parent
@@ -485,8 +547,18 @@ class FunctionCallStatement(override var target: IdentifierReference,
        args.forEach { it.linkParents(this) }
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        if(node===target)
+            target = replacement as IdentifierReference
+        else {
+            val idx = args.indexOfFirst { it===node }
+            args[idx] = replacement as Expression
+        }
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
        return "FunctionCallStatement(target=$target, pos=$position)"
@@ -495,22 +567,20 @@ class FunctionCallStatement(override var target: IdentifierReference,

 class InlineAssembly(val assembly: String, override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = true

    override fun linkParents(parent: Node) {
        this.parent = parent
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) = throw FatalAstException("can't replace here")
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

 class AnonymousScope(override var statements: MutableList<Statement>,
                     override val position: Position) : INameScope, Statement() {
    override val name: String
    override lateinit var parent: Node
-    override val expensiveToInline
-        get() = statements.any { it.expensiveToInline }

    companion object {
        private var sequenceNumber = 1
@@ -526,28 +596,27 @@ class AnonymousScope(override var statements: MutableList<Statement>,
        statements.forEach { it.linkParents(this) }
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Statement)
+        val idx = statements.indexOfFirst { it===node }
+        statements[idx] = replacement
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

 class NopStatement(override val position: Position): Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = false

    override fun linkParents(parent: Node) {
        this.parent = parent
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) = throw FatalAstException("can't replace here")
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
-
-    companion object {
-        fun insteadOf(stmt: Statement): NopStatement {
-            val nop = NopStatement(stmt.position)
-            nop.parent = stmt.parent
-            return nop
-        }
-    }
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

 // the subroutine class covers both the normal user-defined subroutines,
@@ -558,20 +627,13 @@ class Subroutine(override val name: String,
                 val returntypes: List<DataType>,
                 val asmParameterRegisters: List<RegisterOrStatusflag>,
                 val asmReturnvaluesRegisters: List<RegisterOrStatusflag>,
-                 val asmClobbers: Set<Register>,
+                 val asmClobbers: Set<CpuRegister>,
                 val asmAddress: Int?,
                 val isAsmSubroutine: Boolean,
                 override var statements: MutableList<Statement>,
                 override val position: Position) : Statement(), INameScope {

-    var keepAlways: Boolean = false
-    override val expensiveToInline
-            get() = statements.any { it.expensiveToInline }
-
    override lateinit var parent: Node
-    val calledBy = mutableListOf<Node>()
-    val calls = mutableSetOf<Subroutine>()
-
    val scopedname: String by lazy { makeScopedName(name) }

    override fun linkParents(parent: Node) {
@@ -580,13 +642,23 @@ class Subroutine(override val name: String,
        statements.forEach { it.linkParents(this) }
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Statement)
+        val idx = statements.indexOfFirst { it===node }
+        statements[idx] = replacement
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
        return "Subroutine(name=$name, parameters=$parameters, returntypes=$returntypes, ${statements.size} statements, address=$asmAddress)"
    }

+    fun regXasResult() = asmReturnvaluesRegisters.any { it.registerOrPair in setOf(RegisterOrPair.X, RegisterOrPair.AX, RegisterOrPair.XY) }
+    fun regXasParam() = asmParameterRegisters.any { it.registerOrPair in setOf(RegisterOrPair.X, RegisterOrPair.AX, RegisterOrPair.XY) }
+
    fun amountOfRtsInAsm(): Int = statements
            .asSequence()
            .filter { it is InlineAssembly }
@@ -603,6 +675,10 @@ open class SubroutineParameter(val name: String,
    override fun linkParents(parent: Node) {
        this.parent = parent
    }
+
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        throw FatalAstException("can't replace anything in a subroutineparameter node")
+    }
 }

 class IfStatement(var condition: Expression,
@@ -610,8 +686,6 @@ class IfStatement(var condition: Expression,
                  var elsepart: AnonymousScope,
                  override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline: Boolean
-        get() = truepart.expensiveToInline || elsepart.expensiveToInline

    override fun linkParents(parent: Node) {
        this.parent = parent
@@ -620,8 +694,19 @@ class IfStatement(var condition: Expression,
        elsepart.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===condition -> condition = replacement as Expression
+            node===truepart -> truepart = replacement as AnonymousScope
+            node===elsepart -> elsepart = replacement as AnonymousScope
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
+
 }

 class BranchStatement(var condition: BranchCondition,
@@ -629,8 +714,6 @@ class BranchStatement(var condition: BranchCondition,
                      var elsepart: AnonymousScope,
                      override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline: Boolean
-        get() = truepart.expensiveToInline || elsepart.expensiveToInline

    override fun linkParents(parent: Node) {
        this.parent = parent
@@ -638,44 +721,57 @@ class BranchStatement(var condition: BranchCondition,
        elsepart.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===truepart -> truepart = replacement as AnonymousScope
+            node===elsepart -> elsepart = replacement as AnonymousScope
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
+
 }

-class ForLoop(val loopRegister: Register?,
-              var loopVar: IdentifierReference?,
+class ForLoop(var loopVar: IdentifierReference,
              var iterable: Expression,
              var body: AnonymousScope,
              override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = true

    override fun linkParents(parent: Node) {
        this.parent=parent
-        loopVar?.linkParents(this)
+        loopVar.linkParents(this)
        iterable.linkParents(this)
        body.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===loopVar -> loopVar = replacement as IdentifierReference
+            node===iterable -> iterable = replacement as Expression
+            node===body -> body = replacement as AnonymousScope
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    override fun toString(): String {
-        return "ForLoop(loopVar: $loopVar, loopReg: $loopRegister, iterable: $iterable, pos=$position)"
+        return "ForLoop(loopVar: $loopVar, iterable: $iterable, pos=$position)"
    }

-    fun loopVarDt(program: Program): InferredTypes.InferredType {
-        val lv = loopVar
-        return if(loopRegister!=null) InferredTypes.InferredType.known(DataType.UBYTE)
-                else lv?.inferType(program) ?: InferredTypes.InferredType.unknown()
-    }
+    fun loopVarDt(program: Program) = loopVar.inferType(program)
 }

 class WhileLoop(var condition: Expression,
                var body: AnonymousScope,
                override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = true

    override fun linkParents(parent: Node) {
        this.parent = parent
@@ -683,28 +779,45 @@ class WhileLoop(var condition: Expression,
        body.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===condition -> condition = replacement as Expression
+            node===body -> body = replacement as AnonymousScope
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

-class ForeverLoop(var body: AnonymousScope, override val position: Position) : Statement() {
+class RepeatLoop(var iterations: Expression?, var body: AnonymousScope, override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = true

    override fun linkParents(parent: Node) {
        this.parent = parent
+        iterations?.linkParents(this)
        body.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===iterations -> iterations = replacement as Expression
+            node===body -> body = replacement as AnonymousScope
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

-class RepeatLoop(var body: AnonymousScope,
-                 var untilCondition: Expression,
-                 override val position: Position) : Statement() {
+class UntilLoop(var body: AnonymousScope,
+                var untilCondition: Expression,
+                override val position: Position) : Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline = true

    override fun linkParents(parent: Node) {
        this.parent = parent
@@ -712,15 +825,23 @@ class RepeatLoop(var body: AnonymousScope,
        body.linkParents(this)
    }

-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun replaceChildNode(node: Node, replacement: Node) {
+        when {
+            node===untilCondition -> untilCondition = replacement as Expression
+            node===body -> body = replacement as AnonymousScope
+            else -> throw FatalAstException("invalid replace")
+        }
+        replacement.parent = this
+    }
+
    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

 class WhenStatement(var condition: Expression,
                    var choices: MutableList<WhenChoice>,
                    override val position: Position): Statement() {
    override lateinit var parent: Node
-    override val expensiveToInline: Boolean = true

    override fun linkParents(parent: Node) {
        this.parent = parent
@@ -728,6 +849,16 @@ class WhenStatement(var condition: Expression,
        choices.forEach { it.linkParents(this) }
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        if(node===condition)
+            condition = replacement as Expression
+        else {
+            val idx = choices.withIndex().find { it.value===node }!!.index
+            choices[idx] = replacement as WhenChoice
+        }
+        replacement.parent = this
+    }
+
    fun choiceValues(program: Program): List<Pair<List<Int>?, WhenChoice>> {
        // only gives sensible results when the choices are all valid (constant integers)
        val result = mutableListOf<Pair<List<Int>?, WhenChoice>>()
@@ -746,7 +877,7 @@ class WhenStatement(var condition: Expression,
    }

    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }

 class WhenChoice(var values: List<Expression>?,           // if null,  this is the 'else' part
@@ -760,12 +891,18 @@ class WhenChoice(var values: List<Expression>?,           // if null,  this is t
        this.parent = parent
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is AnonymousScope && node===statements)
+        statements = replacement
+        replacement.parent = this
+    }
+
    override fun toString(): String {
        return "Choice($values at $position)"
    }

    fun accept(visitor: IAstVisitor) = visitor.visit(this)
-    fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }


@@ -774,18 +911,24 @@ class StructDecl(override val name: String,
                 override val position: Position): Statement(), INameScope {

    override lateinit var parent: Node
-    override val expensiveToInline: Boolean = true

    override fun linkParents(parent: Node) {
        this.parent = parent
        this.statements.forEach { it.linkParents(this) }
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Statement)
+        val idx = statements.indexOfFirst { it===node }
+        statements[idx] = replacement
+        replacement.parent = this
+    }
+
    val numberOfElements: Int
        get() = this.statements.size

    override fun accept(visitor: IAstVisitor) = visitor.visit(this)
-    override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)

    fun nameOfFirstMember() = (statements.first() as VarDecl).name
 }
@@ -798,10 +941,16 @@ class DirectMemoryWrite(var addressExpression: Expression, override val position
        this.addressExpression.linkParents(this)
    }

+    override fun replaceChildNode(node: Node, replacement: Node) {
+        require(replacement is Expression && node===addressExpression)
+        addressExpression = replacement
+        replacement.parent = this
+    }
+
    override fun toString(): String {
        return "DirectMemoryWrite($addressExpression)"
    }

    fun accept(visitor: IAstVisitor) = visitor.visit(this)
-    fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
+    fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
 }
@@ -0,0 +1,157 @@
+package prog8.compiler
+
+import prog8.ast.IFunctionCall
+import prog8.ast.Node
+import prog8.ast.Program
+import prog8.ast.base.*
+import prog8.ast.expressions.*
+import prog8.ast.processing.AstWalker
+import prog8.ast.processing.IAstModification
+import prog8.ast.statements.*
+
+
+internal class BeforeAsmGenerationAstChanger(val program: Program, val errors: ErrorReporter) : AstWalker() {
+
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
+        subroutineVariables.add(Pair(decl.name, decl))
+        if (decl.value == null && !decl.autogeneratedDontRemove && decl.type == VarDeclType.VAR && decl.datatype in NumericDatatypes) {
+            // a numeric vardecl without an initial value is initialized with zero.
+            decl.value = decl.zeroElementValue()
+        }
+        return noModifications
+    }
+
+    override fun after(assignment: Assignment, parent: Node): Iterable<IAstModification> {
+        // Try to replace A = B <operator> Something  by A= B, A = A <operator> Something
+        // this triggers the more efficent augmented assignment code generation more often.
+        if(!assignment.isAugmentable
+                && assignment.target.identifier != null
+                && assignment.target.isNotMemory(program.namespace)) {
+            val binExpr = assignment.value as? BinaryExpression
+            if(binExpr!=null && binExpr.operator !in comparisonOperators) {
+                if(binExpr.left !is BinaryExpression) {
+                    val assignLeft = Assignment(assignment.target, binExpr.left, assignment.position)
+                    return listOf(
+                            IAstModification.InsertBefore(assignment, assignLeft, parent),
+                            IAstModification.ReplaceNode(binExpr.left, assignment.target.toExpression(), binExpr))
+                }
+            }
+        }
+        return noModifications
+    }
+
+    private val subroutineVariables = mutableListOf<Pair<String, VarDecl>>()
+
+    override fun before(subroutine: Subroutine, parent: Node): Iterable<IAstModification> {
+        subroutineVariables.clear()
+        return noModifications
+    }
+
+    override fun after(scope: AnonymousScope, parent: Node): Iterable<IAstModification> {
+        val decls = scope.statements.filterIsInstance<VarDecl>()
+        subroutineVariables.addAll(decls.map { Pair(it.name, it) })
+
+        val sub = scope.definingSubroutine()
+        if (sub != null) {
+            // move vardecls of the scope into the upper scope. Make sure the position remains the same!
+            val numericVarsWithValue = decls.filter { it.value != null && it.datatype in NumericDatatypes }
+            val replaceVardecls =numericVarsWithValue.map {
+                val initValue = it.value!!  // assume here that value has always been set by now
+                it.value = null     // make sure no value init assignment for this vardecl will be created later (would be superfluous)
+                val target = AssignTarget(IdentifierReference(listOf(it.name), it.position), null, null, it.position)
+                val assign = Assignment(target, initValue, it.position)
+                initValue.parent = assign
+                IAstModification.ReplaceNode(it, assign, scope)
+            }
+            val moveVardeclsUp = decls.map { IAstModification.InsertFirst(it, sub) }
+            return replaceVardecls + moveVardeclsUp
+        }
+        return noModifications
+    }
+
+    override fun after(subroutine: Subroutine, parent: Node): Iterable<IAstModification> {
+        val firstDeclarations = mutableMapOf<String, VarDecl>()
+        for(decl in subroutineVariables) {
+            val existing = firstDeclarations[decl.first]
+            if(existing!=null && existing !== decl.second) {
+                errors.err("variable ${decl.first} already defined in subroutine ${subroutine.name} at ${existing.position}", decl.second.position)
+            } else {
+                firstDeclarations[decl.first] = decl.second
+            }
+        }
+
+
+        // add the implicit return statement at the end (if it's not there yet), but only if it's not a kernel routine.
+        // and if an assembly block doesn't contain a rts/rti, and some other situations.
+        val mods = mutableListOf<IAstModification>()
+        val returnStmt = Return(null, subroutine.position)
+        if (subroutine.asmAddress == null
+                && subroutine.statements.isNotEmpty()
+                && subroutine.amountOfRtsInAsm() == 0
+                && subroutine.statements.lastOrNull { it !is VarDecl } !is Return
+                && subroutine.statements.last() !is Subroutine) {
+            mods += IAstModification.InsertLast(returnStmt, subroutine)
+        }
+
+        // precede a subroutine with a return to avoid falling through into the subroutine from code above it
+        val outerScope = subroutine.definingScope()
+        val outerStatements = outerScope.statements
+        val subroutineStmtIdx = outerStatements.indexOf(subroutine)
+        if (subroutineStmtIdx > 0
+                && outerStatements[subroutineStmtIdx - 1] !is Jump
+                && outerStatements[subroutineStmtIdx - 1] !is Subroutine
+                && outerStatements[subroutineStmtIdx - 1] !is Return
+                && outerScope !is Block) {
+            mods += IAstModification.InsertAfter(outerStatements[subroutineStmtIdx - 1], returnStmt, outerScope as Node)
+        }
+
+        return mods
+    }
+
+    override fun after(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> {
+        // see if we can remove superfluous typecasts (outside of expressions)
+        // such as casting byte<->ubyte,  word<->uword
+        // Also the special typecast of a reference type (str, array) to an UWORD will be changed into address-of.
+        val sourceDt = typecast.expression.inferType(program).typeOrElse(DataType.STRUCT)
+        if (typecast.type in ByteDatatypes && sourceDt in ByteDatatypes
+                || typecast.type in WordDatatypes && sourceDt in WordDatatypes) {
+            if(typecast.parent !is Expression) {
+                return listOf(IAstModification.ReplaceNode(typecast, typecast.expression, parent))
+            }
+        }
+
+
+        // Note: for various reasons (most importantly, code simplicity), the code generator assumes/requires
+        // that the types of assignment values and their target are the same,
+        // and that the types of both operands of a binaryexpression node are the same.
+        // So, it is not easily possible to remove the typecasts that are there to make these conditions true.
+        // The only place for now where we can do this is for:
+        //    asmsub register pair parameter.
+
+        if(typecast.type in WordDatatypes) {
+            val fcall = typecast.parent as? IFunctionCall
+            if (fcall != null) {
+                val sub = fcall.target.targetStatement(program.namespace) as? Subroutine
+                if (sub != null && sub.isAsmSubroutine) {
+                    return listOf(IAstModification.ReplaceNode(typecast, typecast.expression, parent))
+                }
+            }
+        }
+
+        if(sourceDt in PassByReferenceDatatypes) {
+            if(typecast.type==DataType.UWORD) {
+                return listOf(IAstModification.ReplaceNode(
+                        typecast,
+                        AddressOf(typecast.expression as IdentifierReference, typecast.position),
+                        parent
+                ))
+            } else {
+                errors.err("cannot cast pass-by-reference value to type ${typecast.type} (only to UWORD)", typecast.position)
+            }
+        }
+
+        return noModifications
+    }
+}
@@ -4,7 +4,10 @@ import prog8.ast.AstToSourceCode
 import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.statements.Directive
+import prog8.compiler.target.C64Target
 import prog8.compiler.target.CompilationTarget
+import prog8.compiler.target.Cx16Target
+import prog8.optimizer.UnusedCodeRemover
 import prog8.optimizer.constantFold
 import prog8.optimizer.optimizeStatements
 import prog8.optimizer.simplifyExpressions
@@ -12,6 +15,7 @@ import prog8.parser.ModuleImporter
 import prog8.parser.ParsingFailedError
 import prog8.parser.moduleName
 import java.nio.file.Path
+import kotlin.system.exitProcess
 import kotlin.system.measureTimeMillis


@@ -24,108 +28,42 @@ class CompilationResult(val success: Boolean,
 fun compileProgram(filepath: Path,
                   optimize: Boolean,
                   writeAssembly: Boolean,
+                   compilationTarget: String,
                   outputDir: Path): CompilationResult {
+    var programName = ""
    lateinit var programAst: Program
-    var programName: String? = null
-
-    var importedFiles: List<Path> = emptyList()
-    var success=false
-
+    lateinit var importedFiles: List<Path>
    val errors = ErrorReporter()

+    when(compilationTarget) {
+        C64Target.name -> CompilationTarget.instance = C64Target
+        Cx16Target.name -> CompilationTarget.instance = Cx16Target
+        else -> {
+            System.err.println("invalid compilation target")
+            exitProcess(1)
+        }
+    }
+
    try {
        val totalTime = measureTimeMillis {
            // import main module and everything it needs
-            val importer = ModuleImporter(errors)
-            errors.handle()
-
-            println("Parsing...")
-            programAst = Program(moduleName(filepath.fileName), mutableListOf())
-            importer.importModule(programAst, filepath)
-            errors.handle()
-
-            importedFiles = programAst.modules.filter { !it.source.startsWith("@embedded@") }.map{ it.source }
-
-            val compilerOptions = determineCompilationOptions(programAst)
-            if (compilerOptions.launcher == LauncherType.BASIC && compilerOptions.output != OutputType.PRG)
-                throw ParsingFailedError("${programAst.modules.first().position} BASIC launcher requires output type PRG.")
-
-            // if we're producing a PRG or BASIC program, include the c64utils and c64lib libraries
-            if (compilerOptions.launcher == LauncherType.BASIC || compilerOptions.output == OutputType.PRG) {
-                importer.importLibraryModule(programAst, "c64lib")
-                importer.importLibraryModule(programAst, "c64utils")
-            }
-
-            // always import prog8lib and math
-            importer.importLibraryModule(programAst, "math")
-            importer.importLibraryModule(programAst, "prog8lib")
-            errors.handle()
-
-            // perform initial syntax checks and constant folding
-            println("Syntax check...")
-            val time1 = measureTimeMillis {
-                programAst.checkIdentifiers(errors)
-                errors.handle()
-                programAst.makeForeverLoops()
-            }
-
-            //println(" time1: $time1")
-            val time2 = measureTimeMillis {
-                programAst.constantFold(errors)
-                errors.handle()
-            }
-            //println(" time2: $time2")
-            val time3 = measureTimeMillis {
-                programAst.removeNopsFlattenAnonScopes()
-                programAst.reorderStatements()
-                programAst.addTypecasts(errors)
-                errors.handle()
-            }
-            //println(" time3: $time3")
-            val time4 = measureTimeMillis {
-                programAst.checkValid(compilerOptions, errors)          // check if tree is valid
-                errors.handle()
-            }
-            //println(" time4: $time4")
-
-            programAst.checkIdentifiers(errors)
-            errors.handle()
-
-            if (optimize) {
-                // optimize the parse tree
-                println("Optimizing...")
-                while (true) {
-                    // keep optimizing expressions and statements until no more steps remain
-                    val optsDone1 = programAst.simplifyExpressions()
-                    val optsDone2 = programAst.optimizeStatements(errors)
-                    errors.handle()
-                    if (optsDone1 + optsDone2 == 0)
-                        break
-                }
-            }
-
-            programAst.addTypecasts(errors)
-            errors.handle()
-            programAst.removeNopsFlattenAnonScopes()
-            programAst.checkValid(compilerOptions, errors)          // check if final tree is valid
-            errors.handle()
-            programAst.checkRecursion(errors)         // check if there are recursive subroutine calls
-            errors.handle()
+            val (ast, compilationOptions, imported) = parseImports(filepath, errors)
+            programAst = ast
+            importedFiles = imported
+            processAst(programAst, errors, compilationOptions)
+            if (optimize)
+                optimizeAst(programAst, errors)
+            postprocessAst(programAst, errors, compilationOptions)

            // printAst(programAst)

-            if(writeAssembly) {
-                // asm generation directly from the Ast, no need for intermediate code
-                val zeropage = CompilationTarget.machine.getZeropage(compilerOptions)
-                programAst.anonscopeVarsCleanup(errors)
-                errors.handle()
-                val assembly = CompilationTarget.asmGenerator(programAst, zeropage, compilerOptions, outputDir).compileToAssembly(optimize)
-                assembly.assemble(compilerOptions)
-                programName = assembly.name
-            }
-            success = true
+            if(writeAssembly)
+                programName = writeAssembly(programAst, errors, outputDir, optimize, compilationOptions)
        }
+        System.out.flush()
+        System.err.flush()
        println("\nTotal compilation+assemble time: ${totalTime / 1000.0} sec.")
+        return CompilationResult(true, programAst, programName, importedFiles)

    } catch (px: ParsingFailedError) {
        System.err.print("\u001b[91m")  // bright red
@@ -148,16 +86,32 @@ fun compileProgram(filepath: Path,
        System.out.flush()
        throw x
    }
-    return CompilationResult(success, programAst, programName ?: "", importedFiles)
+
+    return CompilationResult(false, Program("failed", mutableListOf()), programName, emptyList())
 }

-fun printAst(programAst: Program) {
-    println()
-    val printer = AstToSourceCode(::print, programAst)
-    printer.visit(programAst)
-    println()
-}
+private fun parseImports(filepath: Path, errors: ErrorReporter): Triple<Program, CompilationOptions, List<Path>> {
+    println("Compiler target: ${CompilationTarget.instance.name}. Parsing...")
+    val importer = ModuleImporter()
+    val programAst = Program(moduleName(filepath.fileName), mutableListOf())
+    importer.importModule(programAst, filepath)
+    errors.handle()

+    val importedFiles = programAst.modules.filter { !it.source.startsWith("@embedded@") }.map { it.source }
+
+    val compilerOptions = determineCompilationOptions(programAst)
+    if (compilerOptions.launcher == LauncherType.BASIC && compilerOptions.output != OutputType.PRG)
+        throw ParsingFailedError("${programAst.modules.first().position} BASIC launcher requires output type PRG.")
+
+    // depending on the machine and compiler options we may have to include some libraries
+    CompilationTarget.instance.machine.importLibs(compilerOptions, importer, programAst)
+
+    // always import prog8lib and math
+    importer.importLibraryModule(programAst, "math")
+    importer.importLibraryModule(programAst, "prog8lib")
+    errors.handle()
+    return Triple(programAst, compilerOptions, importedFiles)
+}

 private fun determineCompilationOptions(program: Program): CompilationOptions {
    val mainModule = program.modules.first()
@@ -171,7 +125,7 @@ private fun determineCompilationOptions(program: Program): CompilationOptions {
            as? Directive)?.args?.single()?.name?.toUpperCase()
    val allOptions = program.modules.flatMap { it.statements }.filter { it is Directive && it.directive == "%option" }.flatMap { (it as Directive).args }.toSet()
    val floatsEnabled = allOptions.any { it.name == "enable_floats" }
-    val zpType: ZeropageType =
+    var zpType: ZeropageType =
            if (zpoption == null)
                if(floatsEnabled) ZeropageType.FLOATSAFE else ZeropageType.KERNALSAFE
            else
@@ -181,6 +135,12 @@ private fun determineCompilationOptions(program: Program): CompilationOptions {
                    ZeropageType.KERNALSAFE
                    // error will be printed by the astchecker
                }
+
+    if (zpType==ZeropageType.FLOATSAFE && CompilationTarget.instance.name == Cx16Target.name) {
+        System.err.println("Warning: Cx16 target must use zp option basicsafe instead of floatsafe")
+        zpType = ZeropageType.BASICSAFE
+    }
+
    val zpReserved = mainModule.statements
            .asSequence()
            .filter { it is Directive && it.directive == "%zpreserved" }
@@ -188,9 +148,93 @@ private fun determineCompilationOptions(program: Program): CompilationOptions {
            .map { it[0].int!!..it[1].int!! }
            .toList()

+    if(outputType!=null && !OutputType.values().any {it.name==outputType}) {
+        System.err.println("invalid output type $outputType")
+        exitProcess(1)
+    }
+    if(launcherType!=null && !LauncherType.values().any {it.name==launcherType}) {
+        System.err.println("invalid launcher type $launcherType")
+        exitProcess(1)
+    }
+
    return CompilationOptions(
            if (outputType == null) OutputType.PRG else OutputType.valueOf(outputType),
            if (launcherType == null) LauncherType.BASIC else LauncherType.valueOf(launcherType),
            zpType, zpReserved, floatsEnabled
    )
 }
+
+private fun processAst(programAst: Program, errors: ErrorReporter, compilerOptions: CompilationOptions) {
+    // perform initial syntax checks and processings
+    println("Processing for target ${CompilationTarget.instance.name}...")
+    programAst.checkIdentifiers(errors)
+    errors.handle()
+    programAst.constantFold(errors)
+    errors.handle()
+    programAst.reorderStatements()
+    programAst.addTypecasts(errors)
+    errors.handle()
+    programAst.variousCleanups()
+    programAst.checkValid(compilerOptions, errors)
+    errors.handle()
+    programAst.checkIdentifiers(errors)
+    errors.handle()
+}
+
+private fun optimizeAst(programAst: Program, errors: ErrorReporter) {
+    // optimize the parse tree
+    println("Optimizing...")
+    while (true) {
+        // keep optimizing expressions and statements until no more steps remain
+        val optsDone1 = programAst.simplifyExpressions()
+        val optsDone2 = programAst.optimizeStatements(errors)
+        programAst.constantFold(errors) // because simplified statements and expressions could give rise to more constants that can be folded away
+        errors.handle()
+        if (optsDone1 + optsDone2 == 0)
+            break
+    }
+
+    val remover = UnusedCodeRemover(errors)
+    remover.visit(programAst)
+    remover.applyModifications()
+    errors.handle()
+}
+
+private fun postprocessAst(programAst: Program, errors: ErrorReporter, compilerOptions: CompilationOptions) {
+    programAst.addTypecasts(errors)
+    errors.handle()
+    programAst.variousCleanups()
+    programAst.checkValid(compilerOptions, errors)          // check if final tree is still valid
+    errors.handle()
+    programAst.checkRecursion(errors)         // check if there are recursive subroutine calls
+    errors.handle()
+    programAst.verifyFunctionArgTypes()
+}
+
+private fun writeAssembly(programAst: Program, errors: ErrorReporter, outputDir: Path,
+                          optimize: Boolean, compilerOptions: CompilationOptions): String {
+    // asm generation directly from the Ast,
+    programAst.processAstBeforeAsmGeneration(errors)
+    errors.handle()
+
+    // printAst(programAst)
+
+    CompilationTarget.instance.machine.initializeZeropage(compilerOptions)
+    val assembly = CompilationTarget.instance.asmGenerator(
+            programAst,
+            errors,
+            CompilationTarget.instance.machine.zeropage,
+            compilerOptions,
+            outputDir).compileToAssembly(optimize)
+    assembly.assemble(compilerOptions)
+    errors.handle()
+    return assembly.name
+}
+
+fun printAst(programAst: Program) {
+    println()
+    val printer = AstToSourceCode(::print, programAst)
+    printer.visit(programAst)
+    println()
+}
+
@@ -8,6 +8,12 @@ class ZeropageDepletedError(message: String) : Exception(message)

 abstract class Zeropage(protected val options: CompilationOptions) {

+    abstract val SCRATCH_B1 : Int      // temp storage for a single byte
+    abstract val SCRATCH_REG : Int     // temp storage for a register
+    abstract val SCRATCH_W1 : Int      // temp storage 1 for a word  $fb+$fc
+    abstract val SCRATCH_W2 : Int      // temp storage 2 for a word  $fb+$fc
+
+
    private val allocations = mutableMapOf<Int, Pair<String, DataType>>()
    val free = mutableListOf<Int>()     // subclasses must set this to the appropriate free locations.

@@ -16,7 +22,7 @@ abstract class Zeropage(protected val options: CompilationOptions) {
    fun available() = if(options.zeropage==ZeropageType.DONTUSE) 0 else free.size

    fun allocate(scopedname: String, datatype: DataType, position: Position?, errors: ErrorReporter): Int {
-        assert(scopedname.isEmpty() || !allocations.values.any { it.first==scopedname } ) {"isSameAs scopedname can't be allocated twice"}
+        assert(scopedname.isEmpty() || !allocations.values.any { it.first==scopedname } ) {"scopedname can't be allocated twice"}

        if(options.zeropage==ZeropageType.DONTUSE)
            throw CompilerException("zero page usage has been disabled")
@@ -30,7 +36,7 @@ abstract class Zeropage(protected val options: CompilationOptions) {
                            if(position!=null)
                                errors.warn("allocated a large value (float) in zeropage", position)
                            else
-                                errors.warn("$scopedname: allocated a large value (float) in zeropage", null)
+                                errors.warn("$scopedname: allocated a large value (float) in zeropage", position ?: Position.DUMMY)
                            5
                        } else throw CompilerException("floating point option not enabled")
                    }
@@ -39,13 +45,13 @@ abstract class Zeropage(protected val options: CompilationOptions) {

        if(free.size > 0) {
            if(size==1) {
-                for(candidate in free.min()!! .. free.max()!!+1) {
+                for(candidate in free.minOrNull()!! .. free.maxOrNull()!!+1) {
                    if(loneByte(candidate))
                        return makeAllocation(candidate, 1, datatype, scopedname)
                }
                return makeAllocation(free[0], 1, datatype, scopedname)
            }
-            for(candidate in free.min()!! .. free.max()!!+1) {
+            for(candidate in free.minOrNull()!! .. free.maxOrNull()!!+1) {
                if (sequentialFree(candidate, size))
                    return makeAllocation(candidate, size, datatype, scopedname)
            }
@@ -1,16 +1,53 @@
 package prog8.compiler.target

 import prog8.ast.Program
+import prog8.ast.base.ErrorReporter
 import prog8.compiler.CompilationOptions
 import prog8.compiler.Zeropage
+import prog8.compiler.target.c64.C64MachineDefinition
+import prog8.compiler.target.c64.Petscii
+import prog8.compiler.target.c64.codegen.AsmGen
+import prog8.compiler.target.cx16.CX16MachineDefinition
 import java.nio.file.Path

+
 internal interface CompilationTarget {
+    val name: String
+    val machine: IMachineDefinition
+    fun encodeString(str: String, altEncoding: Boolean): List<Short>
+    fun decodeString(bytes: List<Short>, altEncoding: Boolean): String
+    fun asmGenerator(program: Program, errors: ErrorReporter, zp: Zeropage, options: CompilationOptions, path: Path): IAssemblyGenerator
+    val initProcName: String?
+    val resetProcName: String?
+
    companion object {
-        lateinit var name: String
-        lateinit var machine: IMachineDefinition
-        lateinit var encodeString: (str: String, altEncoding: Boolean) -> List<Short>
-        lateinit var decodeString: (bytes: List<Short>, altEncoding: Boolean) -> String
-        lateinit var asmGenerator: (Program, Zeropage, CompilationOptions, Path) -> IAssemblyGenerator
+        lateinit var instance: CompilationTarget
    }
 }
+
+
+internal object C64Target: CompilationTarget {
+    override val name = "c64"
+    override val machine = C64MachineDefinition
+    override fun encodeString(str: String, altEncoding: Boolean) =
+            if(altEncoding) Petscii.encodeScreencode(str, true) else Petscii.encodePetscii(str, true)
+    override fun decodeString(bytes: List<Short>, altEncoding: Boolean) =
+            if(altEncoding) Petscii.decodeScreencode(bytes, true) else Petscii.decodePetscii(bytes, true)
+    override fun asmGenerator(program: Program, errors: ErrorReporter, zp: Zeropage, options: CompilationOptions, path: Path) =
+            AsmGen(program, errors, zp, options, path)
+    override val initProcName = "c64.init_system"
+    override val resetProcName = "c64.reset_system"
+}
+
+internal object Cx16Target: CompilationTarget {
+    override val name = "cx16"
+    override val machine = CX16MachineDefinition
+    override fun encodeString(str: String, altEncoding: Boolean) =
+            if(altEncoding) Petscii.encodeScreencode(str, true) else Petscii.encodePetscii(str, true)
+    override fun decodeString(bytes: List<Short>, altEncoding: Boolean) =
+            if(altEncoding) Petscii.decodeScreencode(bytes, true) else Petscii.decodePetscii(bytes, true)
+    override fun asmGenerator(program: Program, errors: ErrorReporter, zp: Zeropage, options: CompilationOptions, path: Path) =
+            AsmGen(program, errors, zp, options, path)
+    override val initProcName = "cx16.init_system"
+    override val resetProcName = "cx16.reset_system"
+}
@@ -1,15 +1,38 @@
 package prog8.compiler.target

+import prog8.ast.Program
 import prog8.compiler.CompilationOptions
 import prog8.compiler.Zeropage
+import prog8.parser.ModuleImporter


-interface IMachineDefinition {
+internal interface IMachineFloat {
+    fun toDouble(): Double
+    fun makeFloatFillAsm(): String
+}
+
+internal enum class CpuType {
+    CPU6502,
+    CPU65c02
+}
+
+internal interface IMachineDefinition {
    val FLOAT_MAX_NEGATIVE: Double
    val FLOAT_MAX_POSITIVE: Double
    val FLOAT_MEM_SIZE: Int
+    val POINTER_MEM_SIZE: Int
+    val ESTACK_LO: Int
+    val ESTACK_HI: Int
+    val BASIC_LOAD_ADDRESS : Int
+    val RAW_LOAD_ADDRESS : Int

    val opcodeNames: Set<String>
+    var zeropage: Zeropage
+    val cpu: CpuType

-    fun getZeropage(compilerOptions: CompilationOptions): Zeropage
+    fun initializeZeropage(compilerOptions: CompilationOptions)
+    fun getFloat(num: Number): IMachineFloat
+    fun getFloatRomConst(number: Double): String?
+    fun importLibs(compilerOptions: CompilationOptions, importer: ModuleImporter, program: Program)
+    fun launchEmulator(programName: String)
 }
@@ -2,6 +2,7 @@ package prog8.compiler.target.c64

 import prog8.compiler.CompilationOptions
 import prog8.compiler.OutputType
+import prog8.compiler.target.CompilationTarget
 import prog8.compiler.target.IAssemblyProgram
 import prog8.compiler.target.generatedLabelPrefix
 import java.nio.file.Path
@@ -14,20 +15,20 @@ class AssemblyProgram(override val name: String, outputDir: Path) : IAssemblyPro
    private val viceMonListFile = outputDir.resolve("$name.vice-mon-list")

    override fun assemble(options: CompilationOptions) {
-        // add "-Wlong-branch"  to see warnings about conversion of branch instructions to jumps
+        // add "-Wlong-branch"  to see warnings about conversion of branch instructions to jumps (default = do this silently)
        val command = mutableListOf("64tass", "--ascii", "--case-sensitive", "--long-branch",
-                "-Wall", "-Wno-strict-bool", "-Wno-shadow", "-Werror", "-Wno-error=long-branch",
+                "-Wall", "-Wno-strict-bool", "-Wno-shadow", // "-Werror",
                "--dump-labels", "--vice-labels", "-l", viceMonListFile.toString(), "--no-monitor")

        val outFile = when (options.output) {
            OutputType.PRG -> {
                command.add("--cbm-prg")
-                println("\nCreating C-64 prg.")
+                println("\nCreating prg for target ${CompilationTarget.instance.name}.")
                prgFile
            }
            OutputType.RAW -> {
                command.add("--nostart")
-                println("\nCreating raw binary.")
+                println("\nCreating raw binary for target ${CompilationTarget.instance.name}.")
                binFile
            }
        }
@@ -1,37 +1,96 @@
 package prog8.compiler.target.c64

-import prog8.compiler.CompilationOptions
-import prog8.compiler.CompilerException
-import prog8.compiler.Zeropage
-import prog8.compiler.ZeropageType
+import prog8.ast.Program
+import prog8.compiler.*
+import prog8.compiler.target.CpuType
 import prog8.compiler.target.IMachineDefinition
-import java.awt.Color
-import java.awt.image.BufferedImage
-import javax.imageio.ImageIO
+import prog8.compiler.target.IMachineFloat
+import prog8.parser.ModuleImporter
+import java.io.IOException
+import java.math.RoundingMode
 import kotlin.math.absoluteValue
 import kotlin.math.pow

-object C64MachineDefinition: IMachineDefinition {
+internal object C64MachineDefinition: IMachineDefinition {
+
+    override val cpu = CpuType.CPU6502

    // 5-byte cbm MFLPT format limitations:
    override val FLOAT_MAX_POSITIVE = 1.7014118345e+38         // bytes: 255,127,255,255,255
    override val FLOAT_MAX_NEGATIVE = -1.7014118345e+38        // bytes: 255,255,255,255,255
    override val FLOAT_MEM_SIZE = 5
-    const val BASIC_LOAD_ADDRESS = 0x0801
-    const val RAW_LOAD_ADDRESS = 0xc000
+    override val POINTER_MEM_SIZE = 2
+    override val BASIC_LOAD_ADDRESS = 0x0801
+    override val RAW_LOAD_ADDRESS = 0xc000

    // the 2*256 byte evaluation stack (on which bytes, words, and even floats are stored during calculations)
    // and some heavily used string constants derived from the two values above
-    const val ESTACK_LO_VALUE       = 0xce00        //  $ce00-$ceff inclusive
-    const val ESTACK_HI_VALUE       = 0xcf00        //  $cf00-$cfff inclusive
-    const val ESTACK_LO_HEX         = "\$ce00"
-    const val ESTACK_LO_PLUS1_HEX   = "\$ce01"
-    const val ESTACK_LO_PLUS2_HEX   = "\$ce02"
-    const val ESTACK_HI_HEX         = "\$cf00"
-    const val ESTACK_HI_PLUS1_HEX   = "\$cf01"
-    const val ESTACK_HI_PLUS2_HEX   = "\$cf02"
+    override val ESTACK_LO = 0xce00        //  $ce00-$ceff inclusive
+    override val ESTACK_HI = 0xcf00        //  $ce00-$ceff inclusive

-    override fun getZeropage(compilerOptions: CompilationOptions) = C64Zeropage(compilerOptions)
+    override lateinit var zeropage: Zeropage
+
+    override fun getFloat(num: Number) = Mflpt5.fromNumber(num)
+
+    override fun getFloatRomConst(number: Double): String? {
+        // try to match the ROM float constants to save memory
+        val mflpt5 = Mflpt5.fromNumber(number)
+        val floatbytes = shortArrayOf(mflpt5.b0, mflpt5.b1, mflpt5.b2, mflpt5.b3, mflpt5.b4)
+        when {
+            floatbytes.contentEquals(shortArrayOf(0x00, 0x00, 0x00, 0x00, 0x00)) -> return "floats.ZERO"        // not a ROM const
+            floatbytes.contentEquals(shortArrayOf(0x82, 0x49, 0x0f, 0xda, 0xa1)) -> return "floats.FL_PIVAL"
+            floatbytes.contentEquals(shortArrayOf(0x90, 0x80, 0x00, 0x00, 0x00)) -> return "floats.FL_N32768"
+            floatbytes.contentEquals(shortArrayOf(0x81, 0x00, 0x00, 0x00, 0x00)) -> return "floats.FL_FONE"
+            floatbytes.contentEquals(shortArrayOf(0x80, 0x35, 0x04, 0xf3, 0x34)) -> return "floats.FL_SQRHLF"
+            floatbytes.contentEquals(shortArrayOf(0x81, 0x35, 0x04, 0xf3, 0x34)) -> return "floats.FL_SQRTWO"
+            floatbytes.contentEquals(shortArrayOf(0x80, 0x80, 0x00, 0x00, 0x00)) -> return "floats.FL_NEGHLF"
+            floatbytes.contentEquals(shortArrayOf(0x80, 0x31, 0x72, 0x17, 0xf8)) -> return "floats.FL_LOG2"
+            floatbytes.contentEquals(shortArrayOf(0x84, 0x20, 0x00, 0x00, 0x00)) -> return "floats.FL_TENC"
+            floatbytes.contentEquals(shortArrayOf(0x9e, 0x6e, 0x6b, 0x28, 0x00)) -> return "floats.FL_NZMIL"
+            floatbytes.contentEquals(shortArrayOf(0x80, 0x00, 0x00, 0x00, 0x00)) -> return "floats.FL_FHALF"
+            floatbytes.contentEquals(shortArrayOf(0x81, 0x38, 0xaa, 0x3b, 0x29)) -> return "floats.FL_LOGEB2"
+            floatbytes.contentEquals(shortArrayOf(0x81, 0x49, 0x0f, 0xda, 0xa2)) -> return "floats.FL_PIHALF"
+            floatbytes.contentEquals(shortArrayOf(0x83, 0x49, 0x0f, 0xda, 0xa2)) -> return "floats.FL_TWOPI"
+            floatbytes.contentEquals(shortArrayOf(0x7f, 0x00, 0x00, 0x00, 0x00)) -> return "floats.FL_FR4"
+            else -> {
+                // attempt to correct for a few rounding issues
+                when (number.toBigDecimal().setScale(10, RoundingMode.HALF_DOWN).toDouble()) {
+                    3.1415926536 -> return "floats.FL_PIVAL"
+                    1.4142135624 -> return "floats.FL_SQRTWO"
+                    0.7071067812 -> return "floats.FL_SQRHLF"
+                    0.6931471806 -> return "floats.FL_LOG2"
+                    else -> {}
+                }
+            }
+        }
+        return null
+    }
+
+    override fun importLibs(compilerOptions: CompilationOptions, importer: ModuleImporter, program: Program) {
+        if (compilerOptions.launcher == LauncherType.BASIC || compilerOptions.output == OutputType.PRG)
+            importer.importLibraryModule(program, "syslib")
+    }
+
+    override fun launchEmulator(programName: String) {
+        for(emulator in listOf("x64sc", "x64")) {
+            println("\nStarting C-64 emulator $emulator...")
+            val cmdline = listOf(emulator, "-silent", "-moncommands", "$programName.vice-mon-list",
+                    "-autostartprgmode", "1", "-autostart-warp", "-autostart", programName + ".prg")
+            val processb = ProcessBuilder(cmdline).inheritIO()
+            val process: Process
+            try {
+                process=processb.start()
+            } catch(x: IOException) {
+                continue  // try the next emulator executable
+            }
+            process.waitFor()
+            break
+        }
+    }
+
+    override fun initializeZeropage(compilerOptions: CompilationOptions) {
+        zeropage = C64Zeropage(compilerOptions)
+    }

    // 6502 opcodes (including aliases and illegal opcodes), these cannot be used as variable or label names
    override val opcodeNames = setOf("adc", "ahx", "alr", "anc", "and", "ane", "arr", "asl", "asr", "axs", "bcc", "bcs",
@@ -45,15 +104,13 @@ object C64MachineDefinition: IMachineDefinition {
            "sta", "stx", "sty", "tas", "tax", "tay", "tsx", "txa", "txs", "tya", "xaa")


-    class C64Zeropage(options: CompilationOptions) : Zeropage(options) {
+    internal class C64Zeropage(options: CompilationOptions) : Zeropage(options) {
+
+        override val SCRATCH_B1 = 0x02      // temp storage for a single byte
+        override val SCRATCH_REG = 0x03     // temp storage for a register
+        override val SCRATCH_W1 = 0xfb      // temp storage 1 for a word  $fb+$fc
+        override val SCRATCH_W2 = 0xfd      // temp storage 2 for a word  $fb+$fc

-        companion object {
-            const val SCRATCH_B1 = 0x02
-            const val SCRATCH_REG = 0x03    // temp storage for a register
-            const val SCRATCH_REG_X = 0xfa    // temp storage for register X (the evaluation stack pointer)
-            const val SCRATCH_W1 = 0xfb     // $fb+$fc
-            const val SCRATCH_W2 = 0xfd     // $fd+$fe
-        }

        override val exitProgramStrategy: ExitProgramStrategy = when (options.zeropage) {
            ZeropageType.BASICSAFE, ZeropageType.DONTUSE -> ExitProgramStrategy.CLEAN_EXIT
@@ -68,7 +125,7 @@ object C64MachineDefinition: IMachineDefinition {
            if (options.zeropage == ZeropageType.FULL) {
                free.addAll(0x04..0xf9)
                free.add(0xff)
-                free.removeAll(listOf(SCRATCH_B1, SCRATCH_REG, SCRATCH_REG_X, SCRATCH_W1, SCRATCH_W1 + 1, SCRATCH_W2, SCRATCH_W2 + 1))
+                free.removeAll(listOf(SCRATCH_B1, SCRATCH_REG, SCRATCH_W1, SCRATCH_W1 + 1, SCRATCH_W2, SCRATCH_W2 + 1))
                free.removeAll(listOf(0xa0, 0xa1, 0xa2, 0x91, 0xc0, 0xc5, 0xcb, 0xf5, 0xf6))        // these are updated by IRQ
            } else {
                if (options.zeropage == ZeropageType.KERNALSAFE || options.zeropage == ZeropageType.FLOATSAFE) {
@@ -90,7 +147,7 @@ object C64MachineDefinition: IMachineDefinition {
                if (options.zeropage == ZeropageType.FLOATSAFE) {
                    // remove the zero page locations used for floating point operations from the free list
                    free.removeAll(listOf(
-                            0x12, 0x26, 0x27, 0x28, 0x29, 0x2a,
+                            0x10, 0x11, 0x12, 0x26, 0x27, 0x28, 0x29, 0x2a,
                            0x57, 0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, 0x60,
                            0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
                            0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72,
@@ -109,19 +166,17 @@ object C64MachineDefinition: IMachineDefinition {
                    free.clear()
                }
            }
-            assert(SCRATCH_B1 !in free)
-            assert(SCRATCH_REG !in free)
-            assert(SCRATCH_REG_X !in free)
-            assert(SCRATCH_W1 !in free)
-            assert(SCRATCH_W2 !in free)
+            require(SCRATCH_B1 !in free)
+            require(SCRATCH_REG !in free)
+            require(SCRATCH_W1 !in free)
+            require(SCRATCH_W2 !in free)

            for (reserved in options.zpReserved)
                reserve(reserved)
        }
    }

-
-    data class Mflpt5(val b0: Short, val b1: Short, val b2: Short, val b3: Short, val b4: Short) {
+    internal data class Mflpt5(val b0: Short, val b1: Short, val b2: Short, val b3: Short, val b4: Short): IMachineFloat {

        companion object {
            val zero = Mflpt5(0, 0, 0, 0, 0)
@@ -168,7 +223,7 @@ object C64MachineDefinition: IMachineDefinition {
            }
        }

-        fun toDouble(): Double {
+        override fun toDouble(): Double {
            if (this == zero) return 0.0
            val exp = b0 - 128
            val sign = (b1.toInt() and 0x80) > 0
@@ -176,91 +231,14 @@ object C64MachineDefinition: IMachineDefinition {
            val result = number.toDouble() * (2.0).pow(exp) / 0x100000000
            return if (sign) -result else result
        }
-    }

-    object Charset {
-        private val normalImg = ImageIO.read(javaClass.getResource("/charset/c64/charset-normal.png"))
-        private val shiftedImg = ImageIO.read(javaClass.getResource("/charset/c64/charset-shifted.png"))
-
-        private fun scanChars(img: BufferedImage): Array<BufferedImage> {
-
-            val transparent = BufferedImage(img.width, img.height, BufferedImage.TYPE_INT_ARGB)
-            transparent.createGraphics().drawImage(img, 0, 0, null)
-
-            val black = Color(0, 0, 0).rgb
-            val nopixel = Color(0, 0, 0, 0).rgb
-            for (y in 0 until transparent.height) {
-                for (x in 0 until transparent.width) {
-                    val col = transparent.getRGB(x, y)
-                    if (col == black)
-                        transparent.setRGB(x, y, nopixel)
-                }
-            }
-
-            val numColumns = transparent.width / 8
-            val charImages = (0..255).map {
-                val charX = it % numColumns
-                val charY = it / numColumns
-                transparent.getSubimage(charX * 8, charY * 8, 8, 8)
-            }
-            return charImages.toTypedArray()
+        override fun makeFloatFillAsm(): String {
+            val b0 = "$" + b0.toString(16).padStart(2, '0')
+            val b1 = "$" + b1.toString(16).padStart(2, '0')
+            val b2 = "$" + b2.toString(16).padStart(2, '0')
+            val b3 = "$" + b3.toString(16).padStart(2, '0')
+            val b4 = "$" + b4.toString(16).padStart(2, '0')
+            return "$b0, $b1, $b2, $b3, $b4"
        }
-
-        val normalChars = scanChars(normalImg)
-        val shiftedChars = scanChars(shiftedImg)
-
-        private val coloredNormalChars = mutableMapOf<Short, Array<BufferedImage>>()
-
-        fun getColoredChar(screenCode: Short, color: Short): BufferedImage {
-            val colorIdx = (color % colorPalette.size).toShort()
-            val chars = coloredNormalChars[colorIdx]
-            if (chars != null)
-                return chars[screenCode.toInt()]
-
-            val coloredChars = mutableListOf<BufferedImage>()
-            val transparent = Color(0, 0, 0, 0).rgb
-            val rgb = colorPalette[colorIdx.toInt()].rgb
-            for (c in normalChars) {
-                val colored = c.copy()
-                for (y in 0 until colored.height)
-                    for (x in 0 until colored.width) {
-                        if (colored.getRGB(x, y) != transparent) {
-                            colored.setRGB(x, y, rgb)
-                        }
-                    }
-                coloredChars.add(colored)
-            }
-            coloredNormalChars[colorIdx] = coloredChars.toTypedArray()
-            return coloredNormalChars.getValue(colorIdx)[screenCode.toInt()]
-        }
-
    }
-
-    private fun BufferedImage.copy(): BufferedImage {
-        val bcopy = BufferedImage(this.width, this.height, this.type)
-        val g = bcopy.graphics
-        g.drawImage(this, 0, 0, null)
-        g.dispose()
-        return bcopy
-    }
-
-    val colorPalette = listOf(         // this is Pepto's Commodore-64 palette  http://www.pepto.de/projects/colorvic/
-            Color(0x000000),  // 0 = black
-            Color(0xFFFFFF),  // 1 = white
-            Color(0x813338),  // 2 = red
-            Color(0x75cec8),  // 3 = cyan
-            Color(0x8e3c97),  // 4 = purple
-            Color(0x56ac4d),  // 5 = green
-            Color(0x2e2c9b),  // 6 = blue
-            Color(0xedf171),  // 7 = yellow
-            Color(0x8e5029),  // 8 = orange
-            Color(0x553800),  // 9 = brown
-            Color(0xc46c71),  // 10 = light red
-            Color(0x4a4a4a),  // 11 = dark grey
-            Color(0x7b7b7b),  // 12 = medium grey
-            Color(0xa9ff9f),  // 13 = light green
-            Color(0x706deb),  // 14 = light blue
-            Color(0xb2b2b2)   // 15 = light grey
-    )
-
 }
@@ -1,8 +1,5 @@
 package prog8.compiler.target.c64.codegen

-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_LO_HEX
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_LO_PLUS1_HEX
-

 // note: see https://wiki.nesdev.com/w/index.php/6502_assembly_optimisations

@@ -13,43 +10,45 @@ fun optimizeAssembly(lines: MutableList<String>): Int {

    var linesByFour = getLinesBy(lines, 4)

-    var removeLines = optimizeUselessStackByteWrites(linesByFour)
-    if(removeLines.isNotEmpty()) {
-        for (i in removeLines.reversed())
-            lines.removeAt(i)
+    var mods = optimizeUselessStackByteWrites(linesByFour)
+    if(mods.isNotEmpty()) {
+        apply(mods, lines)
        linesByFour = getLinesBy(lines, 4)
        numberOfOptimizations++
    }

-    removeLines = optimizeIncDec(linesByFour)
-    if(removeLines.isNotEmpty()) {
-        for (i in removeLines.reversed())
-            lines.removeAt(i)
+    mods = optimizeIncDec(linesByFour)
+    if(mods.isNotEmpty()) {
+        apply(mods, lines)
        linesByFour = getLinesBy(lines, 4)
        numberOfOptimizations++
    }

-    removeLines = optimizeCmpSequence(linesByFour)
-    if(removeLines.isNotEmpty()) {
-        for (i in removeLines.reversed())
-            lines.removeAt(i)
+    mods = optimizeCmpSequence(linesByFour)
+    if(mods.isNotEmpty()) {
+        apply(mods, lines)
        linesByFour = getLinesBy(lines, 4)
        numberOfOptimizations++
    }

-    removeLines = optimizeStoreLoadSame(linesByFour)
-    if(removeLines.isNotEmpty()) {
-        for (i in removeLines.reversed())
-            lines.removeAt(i)
+    mods = optimizeStoreLoadSame(linesByFour)
+    if(mods.isNotEmpty()) {
+        apply(mods, lines)
+        linesByFour = getLinesBy(lines, 4)
+        numberOfOptimizations++
+    }
+
+    mods= optimizeJsrRts(linesByFour)
+    if(mods.isNotEmpty()) {
+        apply(mods, lines)
        linesByFour = getLinesBy(lines, 4)
        numberOfOptimizations++
    }

    var linesByFourteen = getLinesBy(lines, 14)
-    removeLines = optimizeSameAssignments(linesByFourteen)
-    if(removeLines.isNotEmpty()) {
-        for (i in removeLines.reversed())
-            lines.removeAt(i)
+    mods = optimizeSameAssignments(linesByFourteen)
+    if(mods.isNotEmpty()) {
+        apply(mods, lines)
        linesByFourteen = getLinesBy(lines, 14)
        numberOfOptimizations++
    }
@@ -59,7 +58,22 @@ fun optimizeAssembly(lines: MutableList<String>): Int {
    return numberOfOptimizations
 }

-fun optimizeCmpSequence(linesByFour: List<List<IndexedValue<String>>>): List<Int> {
+private class Modification(val lineIndex: Int, val remove: Boolean, val replacement: String?)
+
+private fun apply(modifications: List<Modification>, lines: MutableList<String>) {
+    for (modification in modifications.sortedBy { it.lineIndex }.reversed()) {
+        if(modification.remove)
+            lines.removeAt(modification.lineIndex)
+        else
+            lines[modification.lineIndex] = modification.replacement!!
+    }
+}
+
+private fun getLinesBy(lines: MutableList<String>, windowSize: Int) =
+// all lines (that aren't empty or comments) in sliding windows of certain size
+        lines.withIndex().filter { it.value.isNotBlank() && !it.value.trimStart().startsWith(';') }.windowed(windowSize, partialWindows = false)
+
+private fun optimizeCmpSequence(linesByFour: List<List<IndexedValue<String>>>): List<Modification> {
    // the when statement (on bytes) generates a sequence of:
    //	 lda $ce01,x
    //	 cmp #$20
@@ -68,42 +82,42 @@ fun optimizeCmpSequence(linesByFour: List<List<IndexedValue<String>>>): List<Int
    //	 cmp #$21
    //	 beq  check_prog8_s73choice_33
    // the repeated lda can be removed
-    val removeLines = mutableListOf<Int>()
+    val mods = mutableListOf<Modification>()
    for(lines in linesByFour) {
-        if(lines[0].value.trim()=="lda  $ESTACK_LO_PLUS1_HEX,x" &&
+        if(lines[0].value.trim()=="lda  P8ESTACK_LO+1,x" &&
                lines[1].value.trim().startsWith("cmp ") &&
                lines[2].value.trim().startsWith("beq ") &&
-                lines[3].value.trim()=="lda  $ESTACK_LO_PLUS1_HEX,x") {
-            removeLines.add(lines[3].index) // remove the second lda
+                lines[3].value.trim()=="lda  P8ESTACK_LO+1,x") {
+            mods.add(Modification(lines[3].index, true, null)) // remove the second lda
        }
    }
-    return removeLines
+    return mods
 }

-fun optimizeUselessStackByteWrites(linesByFour: List<List<IndexedValue<String>>>): List<Int> {
+private fun optimizeUselessStackByteWrites(linesByFour: List<List<IndexedValue<String>>>): List<Modification> {
    // sta on stack, dex, inx, lda from stack -> eliminate this useless stack byte write
    // this is a lot harder for word values because the instruction sequence varies.
-    val removeLines = mutableListOf<Int>()
+    val mods = mutableListOf<Modification>()
    for(lines in linesByFour) {
-        if(lines[0].value.trim()=="sta  $ESTACK_LO_HEX,x" &&
+        if(lines[0].value.trim()=="sta  P8ESTACK_LO,x" &&
                lines[1].value.trim()=="dex" &&
                lines[2].value.trim()=="inx" &&
-                lines[3].value.trim()=="lda  $ESTACK_LO_HEX,x") {
-            removeLines.add(lines[1].index)
-            removeLines.add(lines[2].index)
-            removeLines.add(lines[3].index)
+                lines[3].value.trim()=="lda  P8ESTACK_LO,x") {
+            mods.add(Modification(lines[1].index, true, null))
+            mods.add(Modification(lines[2].index, true, null))
+            mods.add(Modification(lines[3].index, true, null))
        }
    }
-    return removeLines
+    return mods
 }

-fun optimizeSameAssignments(linesByFourteen: List<List<IndexedValue<String>>>): List<Int> {
+private fun optimizeSameAssignments(linesByFourteen: List<List<IndexedValue<String>>>): List<Modification> {

    // optimize sequential assignments of the isSameAs value to various targets (bytes, words, floats)
    // the float one is the one that requires 2*7=14 lines of code to check...
    // @todo a better place to do this is in the Compiler instead and transform the Ast, or the AsmGen, and never even create the inefficient asm in the first place...

-    val removeLines = mutableListOf<Int>()
+    val mods = mutableListOf<Modification>()
    for (pair in linesByFourteen) {
        val first = pair[0].value.trimStart()
        val second = pair[1].value.trimStart()
@@ -122,8 +136,8 @@ fun optimizeSameAssignments(linesByFourteen: List<List<IndexedValue<String>>>):
            val fourthvalue = sixth.substring(4)
            if(firstvalue==thirdvalue && secondvalue==fourthvalue) {
                // lda/ldy   sta/sty   twice the isSameAs word -->  remove second lda/ldy pair (fifth and sixth lines)
-                removeLines.add(pair[4].index)
-                removeLines.add(pair[5].index)
+                mods.add(Modification(pair[4].index, true, null))
+                mods.add(Modification(pair[5].index, true, null))
            }
        }

@@ -132,12 +146,13 @@ fun optimizeSameAssignments(linesByFourteen: List<List<IndexedValue<String>>>):
            val secondvalue = third.substring(4)
            if(firstvalue==secondvalue) {
                // lda value / sta ? / lda isSameAs-value / sta ?  -> remove second lda (third line)
-                removeLines.add(pair[2].index)
+                mods.add(Modification(pair[2].index, true, null))
            }
        }

        if(first.startsWith("lda") && second.startsWith("ldy") && third.startsWith("sta") && fourth.startsWith("sty") &&
-                fifth.startsWith("lda") && sixth.startsWith("ldy") && seventh.startsWith("jsr  c64flt.copy_float")) {
+                fifth.startsWith("lda") && sixth.startsWith("ldy") &&
+                (seventh.startsWith("jsr  floats.copy_float") || seventh.startsWith("jsr  cx16flt.copy_float"))) {

            val nineth = pair[8].value.trimStart()
            val tenth = pair[9].value.trimStart()
@@ -147,28 +162,25 @@ fun optimizeSameAssignments(linesByFourteen: List<List<IndexedValue<String>>>):
            val fourteenth = pair[13].value.trimStart()

            if(eighth.startsWith("lda") && nineth.startsWith("ldy") && tenth.startsWith("sta") && eleventh.startsWith("sty") &&
-                    twelveth.startsWith("lda") && thirteenth.startsWith("ldy") && fourteenth.startsWith("jsr  c64flt.copy_float")) {
+                    twelveth.startsWith("lda") && thirteenth.startsWith("ldy") &&
+                    (fourteenth.startsWith("jsr  floats.copy_float") || fourteenth.startsWith("jsr  cx16flt.copy_float"))) {

                if(first.substring(4) == eighth.substring(4) && second.substring(4)==nineth.substring(4)) {
                    // identical float init
-                    removeLines.add(pair[7].index)
-                    removeLines.add(pair[8].index)
-                    removeLines.add(pair[9].index)
-                    removeLines.add(pair[10].index)
+                    mods.add(Modification(pair[7].index, true, null))
+                    mods.add(Modification(pair[8].index, true, null))
+                    mods.add(Modification(pair[9].index, true, null))
+                    mods.add(Modification(pair[10].index, true, null))
                }
            }
        }
    }
-    return removeLines
+    return mods
 }

-private fun getLinesBy(lines: MutableList<String>, windowSize: Int) =
-// all lines (that aren't empty or comments) in sliding windows of certain size
-        lines.withIndex().filter { it.value.isNotBlank() && !it.value.trimStart().startsWith(';') }.windowed(windowSize, partialWindows = false)
-
-private fun optimizeStoreLoadSame(linesByFour: List<List<IndexedValue<String>>>): List<Int> {
+private fun optimizeStoreLoadSame(linesByFour: List<List<IndexedValue<String>>>): List<Modification> {
    // sta X + lda X,  sty X + ldy X,   stx X + ldx X  -> the second instruction can be eliminated
-    val removeLines = mutableListOf<Int>()
+    val mods = mutableListOf<Modification>()
    for (pair in linesByFour) {
        val first = pair[0].value.trimStart()
        val second = pair[1].value.trimStart()
@@ -186,26 +198,40 @@ private fun optimizeStoreLoadSame(linesByFour: List<List<IndexedValue<String>>>)
            val firstLoc = first.substring(4)
            val secondLoc = second.substring(4)
            if (firstLoc == secondLoc) {
-                removeLines.add(pair[1].index)
+                mods.add(Modification(pair[1].index, true, null))
            }
        }
    }
-    return removeLines
+    return mods
 }

-private fun optimizeIncDec(linesByTwo: List<List<IndexedValue<String>>>): List<Int> {
+private fun optimizeIncDec(linesByFour: List<List<IndexedValue<String>>>): List<Modification> {
    // sometimes, iny+dey / inx+dex / dey+iny / dex+inx sequences are generated, these can be eliminated.
-    val removeLines = mutableListOf<Int>()
-    for (pair in linesByTwo) {
+    val mods = mutableListOf<Modification>()
+    for (pair in linesByFour) {
        val first = pair[0].value
        val second = pair[1].value
        if ((" iny" in first || "\tiny" in first) && (" dey" in second || "\tdey" in second)
                || (" inx" in first || "\tinx" in first) && (" dex" in second || "\tdex" in second)
                || (" dey" in first || "\tdey" in first) && (" iny" in second || "\tiny" in second)
                || (" dex" in first || "\tdex" in first) && (" inx" in second || "\tinx" in second)) {
-            removeLines.add(pair[0].index)
-            removeLines.add(pair[1].index)
+            mods.add(Modification(pair[0].index, true, null))
+            mods.add(Modification(pair[1].index, true, null))
        }
    }
-    return removeLines
+    return mods
+}
+
+private fun optimizeJsrRts(linesByFour: List<List<IndexedValue<String>>>): List<Modification> {
+    // jsr Sub + rts -> jmp Sub
+    val mods = mutableListOf<Modification>()
+    for (pair in linesByFour) {
+        val first = pair[0].value
+        val second = pair[1].value
+        if ((" jsr" in first || "\tjsr" in first ) && (" rts" in second || "\trts" in second)) {
+            mods += Modification(pair[0].index, false, pair[0].value.replace("jsr", "jmp"))
+            mods += Modification(pair[1].index, true, null)
+        }
+    }
+    return mods
 }
@@ -1,750 +0,0 @@
-package prog8.compiler.target.c64.codegen
-
-import prog8.ast.Program
-import prog8.ast.base.*
-import prog8.ast.expressions.*
-import prog8.ast.statements.AssignTarget
-import prog8.ast.statements.Assignment
-import prog8.ast.statements.DirectMemoryWrite
-import prog8.ast.statements.VarDecl
-import prog8.compiler.AssemblyError
-import prog8.compiler.target.c64.C64MachineDefinition
-import prog8.compiler.target.c64.C64MachineDefinition.C64Zeropage
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_HI_HEX
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_LO_HEX
-import prog8.compiler.toHex
-
-
-internal class AssignmentAsmGen(private val program: Program, private val asmgen: AsmGen) {
-
-    internal fun translate(assign: Assignment) {
-        if(assign.aug_op!=null)
-            throw AssemblyError("aug-op assignments should have been transformed to normal ones")
-
-        when(assign.value) {
-            is NumericLiteralValue -> {
-                val numVal = assign.value as NumericLiteralValue
-                when(numVal.type) {
-                    DataType.UBYTE, DataType.BYTE -> assignFromByteConstant(assign.target, numVal.number.toShort())
-                    DataType.UWORD, DataType.WORD -> assignFromWordConstant(assign.target, numVal.number.toInt())
-                    DataType.FLOAT -> assignFromFloatConstant(assign.target, numVal.number.toDouble())
-                    else -> throw AssemblyError("weird numval type")
-                }
-            }
-            is RegisterExpr -> {
-                assignFromRegister(assign.target, (assign.value as RegisterExpr).register)
-            }
-            is IdentifierReference -> {
-                val type = assign.target.inferType(program, assign).typeOrElse(DataType.STRUCT)
-                when(type) {
-                    DataType.UBYTE, DataType.BYTE -> assignFromByteVariable(assign.target, assign.value as IdentifierReference)
-                    DataType.UWORD, DataType.WORD -> assignFromWordVariable(assign.target, assign.value as IdentifierReference)
-                    DataType.FLOAT -> assignFromFloatVariable(assign.target, assign.value as IdentifierReference)
-                    else -> throw AssemblyError("unsupported assignment target type $type")
-                }
-            }
-            is AddressOf -> {
-                val identifier = (assign.value as AddressOf).identifier
-                assignFromAddressOf(assign.target, identifier)
-            }
-            is DirectMemoryRead -> {
-                val read = (assign.value as DirectMemoryRead)
-                when(read.addressExpression) {
-                    is NumericLiteralValue -> {
-                        val address = (read.addressExpression as NumericLiteralValue).number.toInt()
-                        assignFromMemoryByte(assign.target, address, null)
-                    }
-                    is IdentifierReference -> {
-                        assignFromMemoryByte(assign.target, null, read.addressExpression as IdentifierReference)
-                    }
-                    else -> {
-                        asmgen.translateExpression(read.addressExpression)
-                        TODO("read memory byte from result and put that in ${assign.target}")
-                    }
-                }
-            }
-            is PrefixExpression -> {
-                // TODO optimize common cases
-                asmgen.translateExpression(assign.value as PrefixExpression)
-                assignFromEvalResult(assign.target)
-            }
-            is BinaryExpression -> {
-                // TODO optimize common cases
-                asmgen.translateExpression(assign.value as BinaryExpression)
-                assignFromEvalResult(assign.target)
-            }
-            is ArrayIndexedExpression -> {
-                // TODO optimize common cases
-                val arrayExpr = assign.value as ArrayIndexedExpression
-                val arrayDt = arrayExpr.identifier.targetVarDecl(program.namespace)!!.datatype
-                val index = arrayExpr.arrayspec.index
-                if(index is NumericLiteralValue) {
-                    // constant array index value
-                    val arrayVarName = asmgen.asmIdentifierName(arrayExpr.identifier)
-                    val indexValue = index.number.toInt() * ArrayElementTypes.getValue(arrayDt).memorySize()
-                    when (arrayDt) {
-                        DataType.STR, DataType.ARRAY_UB, DataType.ARRAY_B ->
-                            asmgen.out("  lda  $arrayVarName+$indexValue |  sta  $ESTACK_LO_HEX,x |  dex")
-                        DataType.ARRAY_UW, DataType.ARRAY_W ->
-                            asmgen.out("  lda  $arrayVarName+$indexValue |  sta  $ESTACK_LO_HEX,x |  lda  $arrayVarName+$indexValue+1 |  sta  $ESTACK_HI_HEX,x | dex")
-                        DataType.ARRAY_F ->
-                            asmgen.out("  lda  #<$arrayVarName+$indexValue |  ldy  #>$arrayVarName+$indexValue |  jsr  c64flt.push_float")
-                        else ->
-                            throw AssemblyError("weird array type")
-                    }
-                } else {
-                    asmgen.translateArrayIndexIntoA(arrayExpr)
-                    asmgen.readAndPushArrayvalueWithIndexA(arrayDt, arrayExpr.identifier)
-                }
-                assignFromEvalResult(assign.target)
-            }
-            is TypecastExpression -> {
-                val cast = assign.value as TypecastExpression
-                val sourceType = cast.expression.inferType(program)
-                val targetType = assign.target.inferType(program, assign)
-                if(sourceType.isKnown && targetType.isKnown &&
-                        (sourceType.typeOrElse(DataType.STRUCT) in ByteDatatypes && targetType.typeOrElse(DataType.STRUCT) in ByteDatatypes) ||
-                        (sourceType.typeOrElse(DataType.STRUCT) in WordDatatypes && targetType.typeOrElse(DataType.STRUCT) in WordDatatypes)) {
-                    // no need for a type cast
-                    assign.value = cast.expression
-                    translate(assign)
-                } else {
-                    asmgen.translateExpression(assign.value as TypecastExpression)
-                    assignFromEvalResult(assign.target)
-                }
-            }
-            is FunctionCall -> {
-                asmgen.translateExpression(assign.value as FunctionCall)
-                assignFromEvalResult(assign.target)
-            }
-            is ArrayLiteralValue, is StringLiteralValue -> TODO("string/array/struct assignment?")
-            is StructLiteralValue -> throw AssemblyError("struct literal value assignment should have been flattened")
-            is RangeExpr -> throw AssemblyError("range expression should have been changed into array values")
-        }
-    }
-
-    internal fun assignFromEvalResult(target: AssignTarget) {
-        val targetIdent = target.identifier
-        when {
-            target.register!=null -> {
-                if(target.register== Register.X)
-                    throw AssemblyError("can't pop into X register - use variable instead")
-                asmgen.out(" inx | ld${target.register.name.toLowerCase()}  $ESTACK_LO_HEX,x ")
-            }
-            targetIdent!=null -> {
-                val targetName = asmgen.asmIdentifierName(targetIdent)
-                val targetDt = targetIdent.inferType(program).typeOrElse(DataType.STRUCT)
-                when(targetDt) {
-                    DataType.UBYTE, DataType.BYTE -> {
-                        asmgen.out(" inx | lda  $ESTACK_LO_HEX,x  | sta  $targetName")
-                    }
-                    DataType.UWORD, DataType.WORD -> {
-                        asmgen.out("""
-                            inx
-                            lda  $ESTACK_LO_HEX,x
-                            sta  $targetName
-                            lda  $ESTACK_HI_HEX,x
-                            sta  $targetName+1
-                        """)
-                    }
-                    DataType.FLOAT -> {
-                        asmgen.out("""
-                            lda  #<$targetName
-                            ldy  #>$targetName
-                            jsr  c64flt.pop_float
-                        """)
-                    }
-                    else -> throw AssemblyError("weird target variable type $targetDt")
-                }
-            }
-            target.memoryAddress!=null -> {
-                asmgen.out("  inx  | ldy  $ESTACK_LO_HEX,x")
-                storeRegisterInMemoryAddress(Register.Y, target.memoryAddress)
-            }
-            target.arrayindexed!=null -> {
-                val arrayDt = target.arrayindexed!!.identifier.targetVarDecl(program.namespace)!!.datatype
-                val arrayVarName = asmgen.asmIdentifierName(target.arrayindexed!!.identifier)
-                asmgen.translateExpression(target.arrayindexed!!.arrayspec.index)
-                asmgen.out("  inx |  lda  $ESTACK_LO_HEX,x")
-                popAndWriteArrayvalueWithIndexA(arrayDt, arrayVarName)
-            }
-            else -> throw AssemblyError("weird assignment target $target")
-        }
-    }
-
-    internal fun assignFromAddressOf(target: AssignTarget, name: IdentifierReference) {
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        val struct = name.memberOfStruct(program.namespace)
-        val sourceName = if(struct!=null) {
-            // take the address of the first struct member instead
-            val decl = name.targetVarDecl(program.namespace)!!
-            val firstStructMember = struct.nameOfFirstMember()
-            // find the flattened var that belongs to this first struct member
-            val firstVarName = listOf(decl.name, firstStructMember)
-            val firstVar = name.definingScope().lookup(firstVarName, name) as VarDecl
-            firstVar.name
-        } else {
-            asmgen.fixNameSymbols(name.nameInSource.joinToString ("."))
-        }
-
-        when {
-            targetIdent!=null -> {
-                val targetName = asmgen.asmIdentifierName(targetIdent)
-                asmgen.out("""
-                        lda  #<$sourceName
-                        ldy  #>$sourceName
-                        sta  $targetName
-                        sty  $targetName+1
-                    """)
-            }
-            target.memoryAddress!=null -> {
-                TODO("assign address $sourceName to memory word $target")
-            }
-            targetArrayIdx!=null -> {
-                val index = targetArrayIdx.arrayspec.index
-                val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                TODO("assign address $sourceName to array $targetName [ $index ]")
-            }
-            else -> TODO("assign address $sourceName to $target")
-        }
-    }
-
-    internal fun assignFromWordVariable(target: AssignTarget, variable: IdentifierReference) {
-        val sourceName = asmgen.asmIdentifierName(variable)
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        when {
-            targetIdent!=null -> {
-                val targetName = asmgen.asmIdentifierName(targetIdent)
-                asmgen.out("""
-                    lda  $sourceName
-                    ldy  $sourceName+1
-                    sta  $targetName
-                    sty  $targetName+1
-                """)
-            }
-            target.memoryAddress!=null -> {
-                TODO("assign wordvar $sourceName to memory ${target.memoryAddress}")
-            }
-            targetArrayIdx!=null -> {
-                val index = targetArrayIdx.arrayspec.index
-                val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                asmgen.out("  lda  $sourceName |  sta  $ESTACK_LO_HEX,x |  lda  $sourceName+1 |  sta  $ESTACK_HI_HEX,x |  dex")
-                asmgen.translateExpression(index)
-                asmgen.out("  inx |  lda  $ESTACK_LO_HEX,x")
-                val arrayDt = targetArrayIdx.identifier.inferType(program).typeOrElse(DataType.STRUCT)
-                popAndWriteArrayvalueWithIndexA(arrayDt, targetName)
-            }
-            else -> TODO("assign wordvar to $target")
-        }
-    }
-
-    internal fun assignFromFloatVariable(target: AssignTarget, variable: IdentifierReference) {
-        val sourceName = asmgen.asmIdentifierName(variable)
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        when {
-            targetIdent!=null -> {
-                val targetName = asmgen.asmIdentifierName(targetIdent)
-                asmgen.out("""
-                    lda  $sourceName
-                    sta  $targetName
-                    lda  $sourceName+1
-                    sta  $targetName+1
-                    lda  $sourceName+2
-                    sta  $targetName+2
-                    lda  $sourceName+3
-                    sta  $targetName+3
-                    lda  $sourceName+4
-                    sta  $targetName+4
-                """)
-            }
-            targetArrayIdx!=null -> {
-                val index = targetArrayIdx.arrayspec.index
-                val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                asmgen.out("  lda  #<$sourceName |  ldy  #>$sourceName |  jsr  c64flt.push_float")
-                asmgen.translateExpression(index)
-                asmgen.out("  lda  #<$targetName |  ldy  #>$targetName |  jsr  c64flt.pop_float_to_indexed_var")
-            }
-            else -> TODO("assign floatvar to $target")
-        }
-    }
-
-    internal fun assignFromByteVariable(target: AssignTarget, variable: IdentifierReference) {
-        val sourceName = asmgen.asmIdentifierName(variable)
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        when {
-            target.register!=null -> {
-                asmgen.out("  ld${target.register.name.toLowerCase()}  $sourceName")
-            }
-            targetIdent!=null -> {
-                val targetName = asmgen.asmIdentifierName(targetIdent)
-                asmgen.out("""
-                    lda  $sourceName
-                    sta  $targetName
-                    """)
-            }
-            targetArrayIdx!=null -> {
-                val index = targetArrayIdx.arrayspec.index
-                val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                val arrayDt = targetArrayIdx.identifier.inferType(program).typeOrElse(DataType.STRUCT)
-                asmgen.out("  lda  $sourceName |  sta  $ESTACK_LO_HEX,x |  dex")
-                asmgen.translateExpression(index)
-                asmgen.out("  inx |  lda  $ESTACK_LO_HEX,x")
-                popAndWriteArrayvalueWithIndexA(arrayDt, targetName)
-            }
-            target.memoryAddress != null -> {
-                val addressExpr = target.memoryAddress.addressExpression
-                val addressLv = addressExpr as? NumericLiteralValue
-                when {
-                    addressLv != null -> asmgen.out("  lda  $sourceName |  sta  ${addressLv.number.toHex()}")
-                    addressExpr is IdentifierReference -> {
-                        val targetName = asmgen.asmIdentifierName(addressExpr)
-                        asmgen.out("  lda  $sourceName |  sta  $targetName")
-                    }
-                    else -> {
-                        asmgen.translateExpression(addressExpr)
-                        asmgen.out("""
-     inx
-     lda  $ESTACK_LO_HEX,x
-     ldy  $ESTACK_HI_HEX,x
-     sta  (+) +1
-     sty  (+) +2
-     lda  $sourceName
-+    sta  ${'$'}ffff      ; modified              
-                            """)
-                    }
-                }
-            }
-            else -> TODO("assign bytevar to $target")
-        }
-    }
-
-    internal fun assignFromRegister(target: AssignTarget, register: Register) {
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        when {
-            targetIdent!=null -> {
-                val targetName = asmgen.asmIdentifierName(targetIdent)
-                asmgen.out("  st${register.name.toLowerCase()}  $targetName")
-            }
-            target.register!=null -> {
-                when(register) {
-                    Register.A -> when(target.register) {
-                        Register.A -> {}
-                        Register.X -> asmgen.out("  tax")
-                        Register.Y -> asmgen.out("  tay")
-                    }
-                    Register.X -> when(target.register) {
-                        Register.A -> asmgen.out("  txa")
-                        Register.X -> {}
-                        Register.Y -> asmgen.out("  txy")
-                    }
-                    Register.Y -> when(target.register) {
-                        Register.A -> asmgen.out("  tya")
-                        Register.X -> asmgen.out("  tyx")
-                        Register.Y -> {}
-                    }
-                }
-            }
-            target.memoryAddress!=null -> {
-                storeRegisterInMemoryAddress(register, target.memoryAddress)
-            }
-            targetArrayIdx!=null -> {
-                val index = targetArrayIdx.arrayspec.index
-                val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                when (index) {
-                    is NumericLiteralValue -> {
-                        val memindex = index.number.toInt()
-                        when(register) {
-                            Register.A -> asmgen.out("  sta  $targetName+$memindex")
-                            Register.X -> asmgen.out("  stx  $targetName+$memindex")
-                            Register.Y -> asmgen.out("  sty  $targetName+$memindex")
-                        }
-                    }
-                    is RegisterExpr -> {
-                        when(register) {
-                            Register.A -> asmgen.out("  sta  ${C64Zeropage.SCRATCH_B1}")
-                            Register.X -> asmgen.out("  stx  ${C64Zeropage.SCRATCH_B1}")
-                            Register.Y -> asmgen.out("  sty  ${C64Zeropage.SCRATCH_B1}")
-                        }
-                        when(index.register) {
-                            Register.A -> {}
-                            Register.X -> asmgen.out("  txa")
-                            Register.Y -> asmgen.out("  tya")
-                        }
-                        asmgen.out("""
-                            tay
-                            lda  ${C64Zeropage.SCRATCH_B1}
-                            sta  $targetName,y
-                            """)
-                    }
-                    is IdentifierReference -> {
-                        when(register) {
-                            Register.A -> asmgen.out("  sta  ${C64Zeropage.SCRATCH_B1}")
-                            Register.X -> asmgen.out("  stx  ${C64Zeropage.SCRATCH_B1}")
-                            Register.Y -> asmgen.out("  sty  ${C64Zeropage.SCRATCH_B1}")
-                        }
-                        asmgen.out("""
-                            lda  ${asmgen.asmIdentifierName(index)}
-                            tay
-                            lda  ${C64Zeropage.SCRATCH_B1}
-                            sta  $targetName,y
-                        """)
-                    }
-                    else -> {
-                        asmgen.saveRegister(register)
-                        asmgen.translateExpression(index)
-                        asmgen.restoreRegister(register)
-                        when(register) {
-                            Register.A -> asmgen.out("  sta  ${C64Zeropage.SCRATCH_B1}")
-                            Register.X -> asmgen.out("  stx  ${C64Zeropage.SCRATCH_B1}")
-                            Register.Y -> asmgen.out("  sty  ${C64Zeropage.SCRATCH_B1}")
-                        }
-                        asmgen.out("""
-                            inx
-                            lda  $ESTACK_LO_HEX,x
-                            tay
-                            lda  ${C64Zeropage.SCRATCH_B1}
-                            sta  $targetName,y  
-                        """)
-                    }
-                }
-            }
-            else -> TODO("assign register $register to $target")
-        }
-    }
-
-    private fun storeRegisterInMemoryAddress(register: Register, memoryAddress: DirectMemoryWrite) {
-        val addressExpr = memoryAddress.addressExpression
-        val addressLv = addressExpr as? NumericLiteralValue
-        val registerName = register.name.toLowerCase()
-        when {
-            addressLv != null -> asmgen.out("  st$registerName  ${addressLv.number.toHex()}")
-            addressExpr is IdentifierReference -> {
-                val targetName = asmgen.asmIdentifierName(addressExpr)
-                when(register) {
-                    Register.A -> asmgen.out("""
-                        ldy  $targetName
-                        sty  ${C64Zeropage.SCRATCH_W1}
-                        ldy  $targetName+1
-                        sty  ${C64Zeropage.SCRATCH_W1+1}
-                        ldy  #0
-                        sta  (${C64Zeropage.SCRATCH_W1}),y
-                        """)
-                    Register.X -> asmgen.out("""
-                        txa
-                        ldy  $targetName
-                        sty  ${C64Zeropage.SCRATCH_W1}
-                        ldy  $targetName+1
-                        sty  ${C64Zeropage.SCRATCH_W1+1}
-                        ldy  #0
-                        sta  (${C64Zeropage.SCRATCH_W1}),y
-                        """)
-                    Register.Y -> asmgen.out("""
-                        tya
-                        ldy  $targetName
-                        sty  ${C64Zeropage.SCRATCH_W1}
-                        ldy  $targetName+1
-                        sty  ${C64Zeropage.SCRATCH_W1+1}
-                        ldy  #0
-                        sta  (${C64Zeropage.SCRATCH_W1}),y
-                        """)
-                }
-            }
-            else -> {
-                asmgen.saveRegister(register)
-                asmgen.translateExpression(addressExpr)
-                asmgen.restoreRegister(register)
-                when (register) {
-                    Register.A -> asmgen.out("  tay")
-                    Register.X -> throw AssemblyError("can't use X register here")
-                    Register.Y -> {}
-                }
-                asmgen.out("""
-     inx
-     lda  $ESTACK_LO_HEX,x
-     sta  (+) +1
-     lda  $ESTACK_HI_HEX,x
-     sta  (+) +2
-+    sty  ${'$'}ffff      ; modified              
-                            """)
-            }
-        }
-    }
-
-    internal fun assignFromWordConstant(target: AssignTarget, word: Int) {
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        when {
-            targetIdent!=null -> {
-                val targetName = asmgen.asmIdentifierName(targetIdent)
-                if(word ushr 8 == word and 255) {
-                    // lsb=msb
-                    asmgen.out("""
-                    lda  #${(word and 255).toHex()}
-                    sta  $targetName
-                    sta  $targetName+1
-                """)
-                } else {
-                    asmgen.out("""
-                    lda  #<${word.toHex()}
-                    ldy  #>${word.toHex()}
-                    sta  $targetName
-                    sty  $targetName+1
-                """)
-                }
-            }
-            target.memoryAddress!=null -> {
-                TODO("assign word $word to memory ${target.memoryAddress}")
-            }
-            targetArrayIdx!=null -> {
-                val index = targetArrayIdx.arrayspec.index
-                val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                // TODO optimize common cases
-                asmgen.translateExpression(index)
-                asmgen.out("""
-                    inx
-                    lda  $ESTACK_LO_HEX,x
-                    asl  a
-                    tay
-                    lda  #<${word.toHex()}
-                    sta  $targetName,y
-                    lda  #>${word.toHex()}
-                    sta  $targetName+1,y
-                """)
-            }
-            else -> TODO("assign word $word to $target")
-        }
-    }
-
-    internal fun assignFromByteConstant(target: AssignTarget, byte: Short) {
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        when {
-            target.register!=null -> {
-                asmgen.out("  ld${target.register.name.toLowerCase()}  #${byte.toHex()}")
-            }
-            targetIdent!=null -> {
-                val targetName = asmgen.asmIdentifierName(targetIdent)
-                asmgen.out(" lda  #${byte.toHex()} |  sta  $targetName ")
-            }
-            target.memoryAddress!=null -> {
-                asmgen.out("  ldy  #${byte.toHex()}")
-                storeRegisterInMemoryAddress(Register.Y, target.memoryAddress)
-            }
-            targetArrayIdx!=null -> {
-                val index = targetArrayIdx.arrayspec.index
-                val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                // TODO optimize common cases
-                asmgen.translateExpression(index)
-                asmgen.out("""
-                    inx
-                    ldy  $ESTACK_LO_HEX,x
-                    lda  #${byte.toHex()}
-                    sta  $targetName,y
-                """)
-            }
-            else -> TODO("assign byte $byte to $target")
-        }
-    }
-
-    internal fun assignFromFloatConstant(target: AssignTarget, float: Double) {
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        if(float==0.0) {
-            // optimized case for float zero
-            when {
-                targetIdent != null -> {
-                    val targetName = asmgen.asmIdentifierName(targetIdent)
-                    asmgen.out("""
-                            lda  #0
-                            sta  $targetName
-                            sta  $targetName+1
-                            sta  $targetName+2
-                            sta  $targetName+3
-                            sta  $targetName+4
-                        """)
-                }
-                targetArrayIdx!=null -> {
-                    val index = targetArrayIdx.arrayspec.index
-                    val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                    if(index is NumericLiteralValue) {
-                        val indexValue = index.number.toInt() * C64MachineDefinition.FLOAT_MEM_SIZE
-                        asmgen.out("""
-                            lda  #0
-                            sta  $targetName+$indexValue
-                            sta  $targetName+$indexValue+1
-                            sta  $targetName+$indexValue+2
-                            sta  $targetName+$indexValue+3
-                            sta  $targetName+$indexValue+4
-                        """)
-                    } else {
-                        asmgen.translateExpression(index)
-                        asmgen.out("""
-                        inx
-                        lda  $ESTACK_LO_HEX,x
-                        asl  a
-                        asl  a
-                        clc
-                        adc  $ESTACK_LO_HEX,x
-                        tay
-                        lda  #0
-                        sta  $targetName,y
-                        sta  $targetName+1,y
-                        sta  $targetName+2,y
-                        sta  $targetName+3,y
-                        sta  $targetName+4,y
-                    """) // TODO use a subroutine for this
-                    }
-                }
-                else -> TODO("assign float 0.0 to $target")
-            }
-        } else {
-            // non-zero value
-            val constFloat = asmgen.getFloatConst(float)
-            when {
-                targetIdent != null -> {
-                    val targetName = asmgen.asmIdentifierName(targetIdent)
-                    asmgen.out("""
-                            lda  $constFloat
-                            sta  $targetName
-                            lda  $constFloat+1
-                            sta  $targetName+1
-                            lda  $constFloat+2
-                            sta  $targetName+2
-                            lda  $constFloat+3
-                            sta  $targetName+3
-                            lda  $constFloat+4
-                            sta  $targetName+4
-                        """)
-                }
-                targetArrayIdx!=null -> {
-                    val index = targetArrayIdx.arrayspec.index
-                    val arrayVarName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                    if(index is NumericLiteralValue) {
-                        val indexValue = index.number.toInt() * C64MachineDefinition.FLOAT_MEM_SIZE
-                        asmgen.out("""
-                            lda  $constFloat
-                            sta  $arrayVarName+$indexValue
-                            lda  $constFloat+1
-                            sta  $arrayVarName+$indexValue+1
-                            lda  $constFloat+2
-                            sta  $arrayVarName+$indexValue+2
-                            lda  $constFloat+3
-                            sta  $arrayVarName+$indexValue+3
-                            lda  $constFloat+4
-                            sta  $arrayVarName+$indexValue+4
-                        """)
-                    } else {
-                        asmgen.translateArrayIndexIntoA(targetArrayIdx)
-                        asmgen.out("""
-                            sta  ${C64Zeropage.SCRATCH_REG}
-                            asl  a
-                            asl  a
-                            clc
-                            adc  ${C64Zeropage.SCRATCH_REG}
-                            tay
-                            lda  $constFloat
-                            sta  $arrayVarName,y
-                            lda  $constFloat+1
-                            sta  $arrayVarName+1,y
-                            lda  $constFloat+2
-                            sta  $arrayVarName+2,y
-                            lda  $constFloat+3
-                            sta  $arrayVarName+3,y
-                            lda  $constFloat+4
-                            sta  $arrayVarName+4,y
-                        """)        // TODO use a subroutine for this
-                    }
-                }
-                else -> TODO("assign float $float to $target")
-            }
-        }
-    }
-
-    internal fun assignFromMemoryByte(target: AssignTarget, address: Int?, identifier: IdentifierReference?) {
-        val targetIdent = target.identifier
-        val targetArrayIdx = target.arrayindexed
-        if(address!=null) {
-            when {
-                target.register!=null -> {
-                    asmgen.out("  ld${target.register.name.toLowerCase()}  ${address.toHex()}")
-                }
-                targetIdent!=null -> {
-                    val targetName = asmgen.asmIdentifierName(targetIdent)
-                    asmgen.out("""
-                        lda  ${address.toHex()}
-                        sta  $targetName
-                        """)
-                }
-                target.memoryAddress!=null -> {
-                    asmgen.out("  ldy  ${address.toHex()}")
-                    storeRegisterInMemoryAddress(Register.Y, target.memoryAddress)
-                }
-                targetArrayIdx!=null -> {
-                    val index = targetArrayIdx.arrayspec.index
-                    val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                    TODO("assign memory byte at $address to array $targetName [ $index ]")
-                }
-                else -> TODO("assign memory byte $target")
-            }
-        }
-        else if(identifier!=null) {
-            val sourceName = asmgen.asmIdentifierName(identifier)
-            when {
-                target.register!=null -> {
-                    asmgen.out("""
-                        ldy  #0
-                        lda  ($sourceName),y
-                    """)
-                    when(target.register){
-                        Register.A -> {}
-                        Register.X -> asmgen.out("  tax")
-                        Register.Y -> asmgen.out("  tay")
-                    }
-                }
-                targetIdent!=null -> {
-                    val targetName = asmgen.asmIdentifierName(targetIdent)
-                    asmgen.out("""
-                        ldy  #0
-                        lda  ($sourceName),y
-                        sta  $targetName
-                    """)
-                }
-                target.memoryAddress!=null -> {
-                    asmgen.out("  ldy  $sourceName")
-                    storeRegisterInMemoryAddress(Register.Y, target.memoryAddress)
-                }
-                targetArrayIdx!=null -> {
-                    val index = targetArrayIdx.arrayspec.index
-                    val targetName = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                    TODO("assign memory byte $sourceName to array $targetName [ $index ]")
-                }
-                else -> TODO("assign memory byte $target")
-            }
-        }
-    }
-
-    private fun popAndWriteArrayvalueWithIndexA(arrayDt: DataType, variablename: String) {
-        when (arrayDt) {
-            DataType.STR, DataType.ARRAY_UB, DataType.ARRAY_B ->
-                asmgen.out("  tay |  inx |  lda  $ESTACK_LO_HEX,x  | sta  $variablename,y")
-            DataType.ARRAY_UW, DataType.ARRAY_W ->
-                asmgen.out("  asl  a |  tay |  inx |  lda  $ESTACK_LO_HEX,x |  sta  $variablename,y |  lda  $ESTACK_HI_HEX,x |  sta $variablename+1,y")
-            DataType.ARRAY_F ->
-                // index * 5 is done in the subroutine that's called
-                asmgen.out("""
-                    sta  $ESTACK_LO_HEX,x
-                    dex
-                    lda  #<$variablename
-                    ldy  #>$variablename
-                    jsr  c64flt.pop_float_to_indexed_var
-                """)
-            else ->
-                throw AssemblyError("weird array type")
-        }
-    }
-}
@@ -4,11 +4,8 @@ import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.expressions.*
 import prog8.compiler.AssemblyError
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_HI_HEX
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_HI_PLUS1_HEX
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_LO_HEX
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_LO_PLUS1_HEX
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_LO_PLUS2_HEX
+import prog8.compiler.target.CompilationTarget
+import prog8.compiler.target.CpuType
 import prog8.compiler.toHex
 import prog8.functions.BuiltinFunctions
 import kotlin.math.absoluteValue
@@ -19,16 +16,14 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
        when(expression) {
            is PrefixExpression -> translateExpression(expression)
            is BinaryExpression -> translateExpression(expression)
-            is ArrayIndexedExpression -> translatePushFromArray(expression)
+            is ArrayIndexedExpression -> translateExpression(expression)
            is TypecastExpression -> translateExpression(expression)
            is AddressOf -> translateExpression(expression)
            is DirectMemoryRead -> translateExpression(expression)
            is NumericLiteralValue -> translateExpression(expression)
-            is RegisterExpr -> translateExpression(expression)
            is IdentifierReference -> translateExpression(expression)
            is FunctionCall -> translateExpression(expression)
-            is ArrayLiteralValue, is StringLiteralValue -> TODO("string/array/struct assignment?")
-            is StructLiteralValue -> throw AssemblyError("struct literal value assignment should have been flattened")
+            is ArrayLiteralValue, is StringLiteralValue -> throw AssemblyError("no asm gen for string/array literal value assignment - should have been replaced by a variable")
            is RangeExpr -> throw AssemblyError("range expression should have been changed into array values")
        }
    }
@@ -39,18 +34,42 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
        if (builtinFunc != null) {
            asmgen.translateFunctioncallExpression(expression, builtinFunc)
        } else {
-            asmgen.translateFunctionCall(expression)
            val sub = expression.target.targetSubroutine(program.namespace)!!
+            asmgen.translateFunctionCall(expression)
            val returns = sub.returntypes.zip(sub.asmReturnvaluesRegisters)
            for ((_, reg) in returns) {
                if (!reg.stack) {
                    // result value in cpu or status registers, put it on the stack
                    if (reg.registerOrPair != null) {
                        when (reg.registerOrPair) {
-                            RegisterOrPair.A -> asmgen.out("  sta  $ESTACK_LO_HEX,x |  dex")
-                            RegisterOrPair.Y -> asmgen.out("  tya |  sta  $ESTACK_LO_HEX,x |  dex")
-                            RegisterOrPair.AY -> asmgen.out("  sta  $ESTACK_LO_HEX,x |  tya |  sta  $ESTACK_HI_HEX,x |  dex")
-                            RegisterOrPair.X, RegisterOrPair.AX, RegisterOrPair.XY -> throw AssemblyError("can't push X register - use a variable")
+                            RegisterOrPair.A -> asmgen.out("  sta  P8ESTACK_LO,x |  dex")
+                            RegisterOrPair.Y -> asmgen.out("  tya |  sta  P8ESTACK_LO,x |  dex")
+                            RegisterOrPair.AY -> asmgen.out("  sta  P8ESTACK_LO,x |  tya |  sta  P8ESTACK_HI,x |  dex")
+                            RegisterOrPair.X -> {
+                                // return value in X register has been discarded, just push a zero
+                                if(CompilationTarget.instance.machine.cpu==CpuType.CPU65c02)
+                                    asmgen.out("  stz  P8ESTACK_LO,x")
+                                else
+                                    asmgen.out("  lda  #0 |  sta  P8ESTACK_LO,x")
+                                asmgen.out("  dex")
+                            }
+                            RegisterOrPair.AX -> {
+                                // return value in X register has been discarded, just push a zero in this place
+                                asmgen.out("  sta  P8ESTACK_LO,x")
+                                if(CompilationTarget.instance.machine.cpu==CpuType.CPU65c02)
+                                    asmgen.out("  stz  P8ESTACK_HI,x")
+                                else
+                                    asmgen.out("  lda  #0 |  sta  P8ESTACK_HI,x")
+                                asmgen.out("  dex")
+                            }
+                            RegisterOrPair.XY -> {
+                                // return value in X register has been discarded, just push a zero in this place
+                                if(CompilationTarget.instance.machine.cpu==CpuType.CPU65c02)
+                                    asmgen.out("  stz  P8ESTACK_LO,x")
+                                else
+                                    asmgen.out("  lda  #0 |  sta  P8ESTACK_LO,x")
+                                asmgen.out("  tya |  sta  P8ESTACK_HI,x |  dex")
+                            }
                        }
                    }
                    // return value from a statusregister is not put on the stack, it should be acted on via a conditional branch such as if_cc
@@ -65,8 +84,13 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
            DataType.UBYTE -> {
                when(expr.type) {
                    DataType.UBYTE, DataType.BYTE -> {}
-                    DataType.UWORD, DataType.WORD -> asmgen.out("  lda  #0  |  sta  $ESTACK_HI_PLUS1_HEX,x")
-                    DataType.FLOAT -> asmgen.out(" jsr  c64flt.stack_ub2float")
+                    DataType.UWORD, DataType.WORD -> {
+                        if(CompilationTarget.instance.machine.cpu==CpuType.CPU65c02)
+                            asmgen.out("  stz  P8ESTACK_HI+1,x")
+                        else
+                            asmgen.out("  lda  #0  |  sta  P8ESTACK_HI+1,x")
+                    }
+                    DataType.FLOAT -> asmgen.out(" jsr  floats.stack_ub2float")
                    in PassByReferenceDatatypes -> throw AssemblyError("cannot cast to a pass-by-reference datatype")
                    else -> throw AssemblyError("weird type")
                }
@@ -74,8 +98,16 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
            DataType.BYTE -> {
                when(expr.type) {
                    DataType.UBYTE, DataType.BYTE -> {}
-                    DataType.UWORD, DataType.WORD -> asmgen.out("  lda  $ESTACK_LO_PLUS1_HEX,x  |  ${asmgen.signExtendAtoMsb("$ESTACK_HI_PLUS1_HEX,x")}")
-                    DataType.FLOAT -> asmgen.out(" jsr  c64flt.stack_b2float")
+                    DataType.UWORD, DataType.WORD -> {
+                        // sign extend
+                        asmgen.out(""" 
+                            lda  P8ESTACK_LO+1,x
+                            ora  #$7f
+                            bmi  +
+                            lda  #0
+                           sta  P8ESTACK_HI+1,x""")
+                    }
+                    DataType.FLOAT -> asmgen.out(" jsr  floats.stack_b2float")
                    in PassByReferenceDatatypes -> throw AssemblyError("cannot cast to a pass-by-reference datatype")
                    else -> throw AssemblyError("weird type")
                }
@@ -84,7 +116,7 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
                when(expr.type) {
                    DataType.BYTE, DataType.UBYTE -> {}
                    DataType.WORD, DataType.UWORD -> {}
-                    DataType.FLOAT -> asmgen.out(" jsr  c64flt.stack_uw2float")
+                    DataType.FLOAT -> asmgen.out(" jsr  floats.stack_uw2float")
                    in PassByReferenceDatatypes -> throw AssemblyError("cannot cast to a pass-by-reference datatype")
                    else -> throw AssemblyError("weird type")
                }
@@ -93,99 +125,88 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
                when(expr.type) {
                    DataType.BYTE, DataType.UBYTE -> {}
                    DataType.WORD, DataType.UWORD -> {}
-                    DataType.FLOAT -> asmgen.out(" jsr  c64flt.stack_w2float")
+                    DataType.FLOAT -> asmgen.out(" jsr  floats.stack_w2float")
                    in PassByReferenceDatatypes -> throw AssemblyError("cannot cast to a pass-by-reference datatype")
                    else -> throw AssemblyError("weird type")
                }
            }
            DataType.FLOAT -> {
                when(expr.type) {
-                    DataType.UBYTE -> asmgen.out(" jsr  c64flt.stack_float2uw")
-                    DataType.BYTE -> asmgen.out(" jsr  c64flt.stack_float2w")
-                    DataType.UWORD -> asmgen.out(" jsr  c64flt.stack_float2uw")
-                    DataType.WORD -> asmgen.out(" jsr  c64flt.stack_float2w")
+                    DataType.UBYTE -> asmgen.out(" jsr  floats.stack_float2uw")
+                    DataType.BYTE -> asmgen.out(" jsr  floats.stack_float2w")
+                    DataType.UWORD -> asmgen.out(" jsr  floats.stack_float2uw")
+                    DataType.WORD -> asmgen.out(" jsr  floats.stack_float2w")
                    DataType.FLOAT -> {}
                    in PassByReferenceDatatypes -> throw AssemblyError("cannot cast to a pass-by-reference datatype")
                    else -> throw AssemblyError("weird type")
                }
            }
-            in PassByReferenceDatatypes -> throw AssemblyError("cannot case a pass-by-reference datatypes into something else")
+            in PassByReferenceDatatypes -> throw AssemblyError("cannot cast pass-by-reference value into another type")
            else -> throw AssemblyError("weird type")
        }
    }

    private fun translateExpression(expr: AddressOf) {
-        val name = asmgen.asmIdentifierName(expr.identifier)
-        asmgen.out("  lda  #<$name |  sta  $ESTACK_LO_HEX,x |  lda  #>$name  |  sta  $ESTACK_HI_HEX,x  | dex")
+        val name = asmgen.asmVariableName(expr.identifier)
+        asmgen.out("  lda  #<$name |  sta  P8ESTACK_LO,x |  lda  #>$name  |  sta  P8ESTACK_HI,x  | dex")
    }

    private fun translateExpression(expr: DirectMemoryRead) {
        when(expr.addressExpression) {
            is NumericLiteralValue -> {
                val address = (expr.addressExpression as NumericLiteralValue).number.toInt()
-                asmgen.out("  lda  ${address.toHex()} |  sta  $ESTACK_LO_HEX,x |  dex")
+                asmgen.out("  lda  ${address.toHex()} |  sta  P8ESTACK_LO,x |  dex")
            }
            is IdentifierReference -> {
-                val sourceName = asmgen.asmIdentifierName(expr.addressExpression as IdentifierReference)
-                asmgen.out("  lda  $sourceName |  sta  $ESTACK_LO_HEX,x |  dex")
+                // the identifier is a pointer variable, so read the value from the address in it
+                asmgen.loadByteFromPointerIntoA(expr.addressExpression as IdentifierReference)
+                asmgen.out(" sta  P8ESTACK_LO,x |  dex")
            }
            else -> {
                translateExpression(expr.addressExpression)
-                asmgen.out("  jsr  prog8_lib.read_byte_from_address")
-                asmgen.out("  sta  $ESTACK_LO_PLUS1_HEX,x")
+                asmgen.out("  jsr  prog8_lib.read_byte_from_address_on_stack")
+                asmgen.out("  sta  P8ESTACK_LO+1,x")
            }
        }
    }

    private fun translateExpression(expr: NumericLiteralValue) {
        when(expr.type) {
-            DataType.UBYTE, DataType.BYTE -> asmgen.out(" lda  #${expr.number.toHex()}  | sta  $ESTACK_LO_HEX,x  | dex")
+            DataType.UBYTE, DataType.BYTE -> asmgen.out(" lda  #${expr.number.toHex()}  | sta  P8ESTACK_LO,x  | dex")
            DataType.UWORD, DataType.WORD -> asmgen.out("""
                lda  #<${expr.number.toHex()}
-                sta  $ESTACK_LO_HEX,x
+                sta  P8ESTACK_LO,x
                lda  #>${expr.number.toHex()}
-                sta  $ESTACK_HI_HEX,x
+                sta  P8ESTACK_HI,x
                dex
            """)
            DataType.FLOAT -> {
-                val floatConst = asmgen.getFloatConst(expr.number.toDouble())
-                asmgen.out(" lda  #<$floatConst |  ldy  #>$floatConst |  jsr  c64flt.push_float")
+                val floatConst = asmgen.getFloatAsmConst(expr.number.toDouble())
+                asmgen.out(" lda  #<$floatConst |  ldy  #>$floatConst |  jsr  floats.push_float")
            }
            else -> throw AssemblyError("weird type")
        }
    }

-    private fun translateExpression(expr: RegisterExpr) {
-        when(expr.register) {
-            Register.A -> asmgen.out(" sta  $ESTACK_LO_HEX,x | dex")
-            Register.X -> asmgen.out(" txa |  sta  $ESTACK_LO_HEX,x | dex")
-            Register.Y -> asmgen.out(" tya |  sta  $ESTACK_LO_HEX,x | dex")
-        }
-    }
-
    private fun translateExpression(expr: IdentifierReference) {
-        val varname = asmgen.asmIdentifierName(expr)
+        val varname = asmgen.asmVariableName(expr)
        when(expr.inferType(program).typeOrElse(DataType.STRUCT)) {
            DataType.UBYTE, DataType.BYTE -> {
-                asmgen.out("  lda  $varname  |  sta  $ESTACK_LO_HEX,x  |  dex")
+                asmgen.out("  lda  $varname  |  sta  P8ESTACK_LO,x  |  dex")
            }
            DataType.UWORD, DataType.WORD -> {
-                asmgen.out("  lda  $varname  |  sta  $ESTACK_LO_HEX,x  |  lda  $varname+1 |  sta  $ESTACK_HI_HEX,x |  dex")
+                asmgen.out("  lda  $varname  |  sta  P8ESTACK_LO,x  |  lda  $varname+1 |  sta  P8ESTACK_HI,x |  dex")
            }
            DataType.FLOAT -> {
-                asmgen.out(" lda  #<$varname |  ldy  #>$varname|  jsr  c64flt.push_float")
+                asmgen.out(" lda  #<$varname |  ldy  #>$varname|  jsr  floats.push_float")
            }
            in IterableDatatypes -> {
-                asmgen.out("  lda  #<$varname  |  sta  $ESTACK_LO_HEX,x  |  lda  #>$varname |  sta  $ESTACK_HI_HEX,x |  dex")
+                asmgen.out("  lda  #<$varname  |  sta  P8ESTACK_LO,x  |  lda  #>$varname |  sta  P8ESTACK_HI,x |  dex")
            }
            else -> throw AssemblyError("stack push weird variable type $expr")
        }
    }

-    private val optimizedByteMultiplications = setOf(3,5,6,7,9,10,11,12,13,14,15,20,25,40)
-    private val optimizedWordMultiplications = setOf(3,5,6,7,9,10,12,15,20,25,40)
-    private val powersOfTwo = setOf(0,1,2,4,8,16,32,64,128,256)
-
    private fun translateExpression(expr: BinaryExpression) {
        val leftIDt = expr.left.inferType(program)
        val rightIDt = expr.right.inferType(program)
@@ -197,27 +218,80 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
        // see if we can apply some optimized routines
        when(expr.operator) {
            ">>" -> {
-                // bit-shifts are always by a constant number (for now)
                translateExpression(expr.left)
-                val amount = expr.right.constValue(program)!!.number.toInt()
-                when (leftDt) {
-                    DataType.UBYTE -> repeat(amount) { asmgen.out("  lsr  $ESTACK_LO_PLUS1_HEX,x") }
-                    DataType.BYTE -> repeat(amount) { asmgen.out("  lda  $ESTACK_LO_PLUS1_HEX,x |  asl  a |  ror  $ESTACK_LO_PLUS1_HEX,x") }
-                    DataType.UWORD -> repeat(amount) { asmgen.out("  lsr  $ESTACK_HI_PLUS1_HEX,x |  ror  $ESTACK_LO_PLUS1_HEX,x") }
-                    DataType.WORD -> repeat(amount) { asmgen.out("  lda  $ESTACK_HI_PLUS1_HEX,x |  asl a  |  ror  $ESTACK_HI_PLUS1_HEX,x |  ror  $ESTACK_LO_PLUS1_HEX,x") }
-                    else -> throw AssemblyError("weird type")
+                val amount = expr.right.constValue(program)?.number?.toInt()
+                if(amount!=null) {
+                    when (leftDt) {
+                        DataType.UBYTE -> {
+                            if (amount <= 2)
+                                repeat(amount) { asmgen.out(" lsr  P8ESTACK_LO+1,x") }
+                            else {
+                                asmgen.out(" lda  P8ESTACK_LO+1,x")
+                                repeat(amount) { asmgen.out(" lsr  a") }
+                                asmgen.out(" sta  P8ESTACK_LO+1,x")
+                            }
+                        }
+                        DataType.BYTE -> {
+                            if (amount <= 2)
+                                repeat(amount) { asmgen.out(" lda  P8ESTACK_LO+1,x |  asl  a |  ror  P8ESTACK_LO+1,x") }
+                            else {
+                                asmgen.out(" lda  P8ESTACK_LO+1,x |  sta  P8ZP_SCRATCH_B1")
+                                repeat(amount) { asmgen.out(" asl  a |  ror  P8ZP_SCRATCH_B1 |  lda  P8ZP_SCRATCH_B1") }
+                                asmgen.out(" sta  P8ESTACK_LO+1,x")
+                            }
+                        }
+                        DataType.UWORD -> {
+                            var left = amount
+                            while (left >= 7) {
+                                asmgen.out(" jsr  math.shift_right_uw_7")
+                                left -= 7
+                            }
+                            if (left in 0..2)
+                                repeat(left) { asmgen.out(" lsr  P8ESTACK_HI+1,x |  ror  P8ESTACK_LO+1,x") }
+                            else
+                                asmgen.out(" jsr  math.shift_right_uw_$left")
+                        }
+                        DataType.WORD -> {
+                            var left = amount
+                            while (left >= 7) {
+                                asmgen.out(" jsr  math.shift_right_w_7")
+                                left -= 7
+                            }
+                            if (left in 0..2)
+                                repeat(left) { asmgen.out(" lda  P8ESTACK_HI+1,x |  asl a  |  ror  P8ESTACK_HI+1,x |  ror  P8ESTACK_LO+1,x") }
+                            else
+                                asmgen.out(" jsr  math.shift_right_w_$left")
+                        }
+                        else -> throw AssemblyError("weird type")
+                    }
+                    return
                }
-                return
            }
            "<<" -> {
-                // bit-shifts are always by a constant number (for now)
                translateExpression(expr.left)
-                val amount = expr.right.constValue(program)!!.number.toInt()
-                if (leftDt in ByteDatatypes)
-                    repeat(amount) { asmgen.out("  asl  $ESTACK_LO_PLUS1_HEX,x") }
-                else
-                    repeat(amount) { asmgen.out("  asl  $ESTACK_LO_PLUS1_HEX,x |  rol  $ESTACK_HI_PLUS1_HEX,x") }
-                return
+                val amount = expr.right.constValue(program)?.number?.toInt()
+                if(amount!=null) {
+                    if (leftDt in ByteDatatypes) {
+                        if (amount <= 2)
+                            repeat(amount) { asmgen.out("  asl  P8ESTACK_LO+1,x") }
+                        else {
+                            asmgen.out("  lda  P8ESTACK_LO+1,x")
+                            repeat(amount) { asmgen.out("  asl  a") }
+                            asmgen.out("  sta  P8ESTACK_LO+1,x")
+                        }
+                    } else {
+                        var left = amount
+                        while (left >= 7) {
+                            asmgen.out(" jsr  math.shift_left_w_7")
+                            left -= 7
+                        }
+                        if (left in 0..2)
+                            repeat(left) { asmgen.out("  asl  P8ESTACK_LO+1,x |  rol  P8ESTACK_HI+1,x") }
+                        else
+                            asmgen.out(" jsr  math.shift_left_w_$left")
+                    }
+                    return
+                }
            }
            "*" -> {
                val value = expr.right.constValue(program)
@@ -226,40 +300,40 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
                        val amount = value.number.toInt()
                        when(rightDt) {
                            DataType.UBYTE -> {
-                                if(amount in optimizedByteMultiplications) {
+                                if(amount in asmgen.optimizedByteMultiplications) {
                                    translateExpression(expr.left)
-                                    asmgen.out(" jsr  math.mul_byte_$amount")
+                                    asmgen.out(" jsr  math.stack_mul_byte_$amount")
                                    return
                                }
                            }
                            DataType.BYTE -> {
-                                if(amount in optimizedByteMultiplications) {
+                                if(amount in asmgen.optimizedByteMultiplications) {
                                    translateExpression(expr.left)
-                                    asmgen.out(" jsr  math.mul_byte_$amount")
+                                    asmgen.out(" jsr  math.stack_mul_byte_$amount")
                                    return
                                }
-                                if(amount.absoluteValue in optimizedByteMultiplications) {
+                                if(amount.absoluteValue in asmgen.optimizedByteMultiplications) {
                                    translateExpression(expr.left)
-                                    asmgen.out(" jsr  prog8_lib.neg_b |  jsr  math.mul_byte_${amount.absoluteValue}")
+                                    asmgen.out(" jsr  prog8_lib.neg_b |  jsr  math.stack_mul_byte_${amount.absoluteValue}")
                                    return
                                }
                            }
                            DataType.UWORD -> {
-                                if(amount in optimizedWordMultiplications) {
+                                if(amount in asmgen.optimizedWordMultiplications) {
                                    translateExpression(expr.left)
-                                    asmgen.out(" jsr  math.mul_word_$amount")
+                                    asmgen.out(" jsr  math.stack_mul_word_$amount")
                                    return
                                }
                            }
                            DataType.WORD -> {
-                                if(amount in optimizedWordMultiplications) {
+                                if(amount in asmgen.optimizedWordMultiplications) {
                                    translateExpression(expr.left)
-                                    asmgen.out(" jsr  math.mul_word_$amount")
+                                    asmgen.out(" jsr  math.stack_mul_word_$amount")
                                    return
                                }
-                                if(amount.absoluteValue in optimizedWordMultiplications) {
+                                if(amount.absoluteValue in asmgen.optimizedWordMultiplications) {
                                    translateExpression(expr.left)
-                                    asmgen.out(" jsr  prog8_lib.neg_w |  jsr  math.mul_word_${amount.absoluteValue}")
+                                    asmgen.out(" jsr  prog8_lib.neg_w |  jsr  math.stack_mul_word_${amount.absoluteValue}")
                                    return
                                }
                            }
@@ -273,8 +347,10 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
        // the general, non-optimized cases
        translateExpression(expr.left)
        translateExpression(expr.right)
-        if(leftDt!=rightDt)
-            throw AssemblyError("binary operator ${expr.operator} left/right dt not identical")     // is this strictly required always?
+        if((leftDt in ByteDatatypes && rightDt !in ByteDatatypes)
+                || (leftDt in WordDatatypes && rightDt !in WordDatatypes))
+            throw AssemblyError("binary operator ${expr.operator} left/right dt not identical")
+
        when (leftDt) {
            in ByteDatatypes -> translateBinaryOperatorBytes(expr.operator, leftDt)
            in WordDatatypes -> translateBinaryOperatorWords(expr.operator, leftDt)
@@ -292,7 +368,7 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
                when(type) {
                    in ByteDatatypes -> asmgen.out("  jsr  prog8_lib.neg_b")
                    in WordDatatypes -> asmgen.out("  jsr  prog8_lib.neg_w")
-                    DataType.FLOAT -> asmgen.out("  jsr  c64flt.neg_f")
+                    DataType.FLOAT -> asmgen.out("  jsr  floats.neg_f")
                    else -> throw AssemblyError("weird type")
                }
            }
@@ -300,9 +376,9 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
                when(type) {
                    in ByteDatatypes ->
                        asmgen.out("""
-                            lda  $ESTACK_LO_PLUS1_HEX,x
+                            lda  P8ESTACK_LO+1,x
                            eor  #255
-                            sta  $ESTACK_LO_PLUS1_HEX,x
+                            sta  P8ESTACK_LO+1,x
                            """)
                    in WordDatatypes -> asmgen.out("  jsr  prog8_lib.inv_word")
                    else -> throw AssemblyError("weird type")
@@ -319,29 +395,47 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
        }
    }

-    private fun translatePushFromArray(arrayExpr: ArrayIndexedExpression) {
-        // assume *reading* from an array
+    private fun translateExpression(arrayExpr: ArrayIndexedExpression) {
        val index = arrayExpr.arrayspec.index
-        val arrayDt = arrayExpr.identifier.targetVarDecl(program.namespace)!!.datatype
-        val arrayVarName = asmgen.asmIdentifierName(arrayExpr.identifier)
+        val elementDt = arrayExpr.inferType(program).typeOrElse(DataType.STRUCT)
+        val arrayVarName = asmgen.asmVariableName(arrayExpr.identifier)
        if(index is NumericLiteralValue) {
-            val elementDt = ArrayElementTypes.getValue(arrayDt)
            val indexValue = index.number.toInt() * elementDt.memorySize()
            when(elementDt) {
                in ByteDatatypes -> {
-                    asmgen.out("  lda  $arrayVarName+$indexValue |  sta  $ESTACK_LO_HEX,x |  dex")
+                    asmgen.out("  lda  $arrayVarName+$indexValue |  sta  P8ESTACK_LO,x |  dex")
                }
                in WordDatatypes -> {
-                    asmgen.out("  lda  $arrayVarName+$indexValue |  sta  $ESTACK_LO_HEX,x |  lda  $arrayVarName+$indexValue+1 |  sta  $ESTACK_HI_HEX,x |  dex")
+                    asmgen.out("  lda  $arrayVarName+$indexValue |  sta  P8ESTACK_LO,x |  lda  $arrayVarName+$indexValue+1 |  sta  P8ESTACK_HI,x |  dex")
                }
                DataType.FLOAT -> {
-                    asmgen.out("  lda  #<$arrayVarName+$indexValue |  ldy  #>$arrayVarName+$indexValue |  jsr  c64flt.push_float")
+                    asmgen.out("  lda  #<$arrayVarName+$indexValue |  ldy  #>$arrayVarName+$indexValue |  jsr  floats.push_float")
                }
-                else -> throw AssemblyError("weird type")
+                else -> throw AssemblyError("weird element type")
            }
        } else {
-            asmgen.translateArrayIndexIntoA(arrayExpr)
-            asmgen.readAndPushArrayvalueWithIndexA(arrayDt, arrayExpr.identifier)
+            when(elementDt) {
+                in ByteDatatypes -> {
+                    asmgen.loadScaledArrayIndexIntoRegister(arrayExpr, elementDt, CpuRegister.Y)
+                    asmgen.out(" lda  $arrayVarName,y |  sta  P8ESTACK_LO,x |  dex")
+                }
+                in WordDatatypes -> {
+                    asmgen.loadScaledArrayIndexIntoRegister(arrayExpr, elementDt, CpuRegister.Y)
+                    asmgen.out(" lda  $arrayVarName,y |  sta  P8ESTACK_LO,x |  lda  $arrayVarName+1,y |  sta  P8ESTACK_HI,x |  dex")
+                }
+                DataType.FLOAT -> {
+                    asmgen.loadScaledArrayIndexIntoRegister(arrayExpr, elementDt, CpuRegister.A)
+                    asmgen.out("""
+                        ldy  #>$arrayVarName
+                        clc
+                        adc  #<$arrayVarName
+                        bcc  +
+                        iny
+                       jsr  floats.push_float""")
+                }
+                else -> throw AssemblyError("weird dt")
+            }
+
        }
    }

@@ -356,20 +450,21 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
                asmgen.out("  jsr prog8_lib.remainder_ub")
            }
            "+" -> asmgen.out("""
-                lda  $ESTACK_LO_PLUS2_HEX,x
+                lda  P8ESTACK_LO+2,x
                clc
-                adc  $ESTACK_LO_PLUS1_HEX,x
+                adc  P8ESTACK_LO+1,x
                inx
-                sta  $ESTACK_LO_PLUS1_HEX,x
+                sta  P8ESTACK_LO+1,x
                """)
            "-" -> asmgen.out("""
-                lda  $ESTACK_LO_PLUS2_HEX,x
+                lda  P8ESTACK_LO+2,x
                sec
-                sbc  $ESTACK_LO_PLUS1_HEX,x
+                sbc  P8ESTACK_LO+1,x
                inx
-                sta  $ESTACK_LO_PLUS1_HEX,x
+                sta  P8ESTACK_LO+1,x
                """)
-            "<<", ">>" -> throw AssemblyError("bit-shifts not via stack")
+            "<<" -> asmgen.out("  jsr  prog8_lib.shiftleft_b")
+            ">>" -> asmgen.out("  jsr  prog8_lib.shiftright_b")
            "<" -> asmgen.out(if(types==DataType.UBYTE) "  jsr  prog8_lib.less_ub" else "  jsr  prog8_lib.less_b")
            ">" -> asmgen.out(if(types==DataType.UBYTE) "  jsr  prog8_lib.greater_ub" else "  jsr  prog8_lib.greater_b")
            "<=" -> asmgen.out(if(types==DataType.UBYTE) "  jsr  prog8_lib.lesseq_ub" else "  jsr  prog8_lib.lesseq_b")
@@ -418,17 +513,17 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge

    private fun translateBinaryOperatorFloats(operator: String) {
        when(operator) {
-            "**" -> asmgen.out(" jsr  c64flt.pow_f")
-            "*" -> asmgen.out("  jsr  c64flt.mul_f")
-            "/" -> asmgen.out("  jsr  c64flt.div_f")
-            "+" -> asmgen.out("  jsr  c64flt.add_f")
-            "-" -> asmgen.out("  jsr  c64flt.sub_f")
-            "<" -> asmgen.out("  jsr  c64flt.less_f")
-            ">" -> asmgen.out("  jsr  c64flt.greater_f")
-            "<=" -> asmgen.out("  jsr  c64flt.lesseq_f")
-            ">=" -> asmgen.out("  jsr  c64flt.greatereq_f")
-            "==" -> asmgen.out("  jsr  c64flt.equal_f")
-            "!=" -> asmgen.out("  jsr  c64flt.notequal_f")
+            "**" -> asmgen.out(" jsr  floats.pow_f")
+            "*" -> asmgen.out("  jsr  floats.mul_f")
+            "/" -> asmgen.out("  jsr  floats.div_f")
+            "+" -> asmgen.out("  jsr  floats.add_f")
+            "-" -> asmgen.out("  jsr  floats.sub_f")
+            "<" -> asmgen.out("  jsr  floats.less_f")
+            ">" -> asmgen.out("  jsr  floats.greater_f")
+            "<=" -> asmgen.out("  jsr  floats.lesseq_f")
+            ">=" -> asmgen.out("  jsr  floats.greatereq_f")
+            "==" -> asmgen.out("  jsr  floats.equal_f")
+            "!=" -> asmgen.out("  jsr  floats.notequal_f")
            "%", "<<", ">>", "&", "^", "|", "and", "or", "xor" -> throw AssemblyError("requires integer datatype")
            else -> throw AssemblyError("invalid operator $operator")
        }
@@ -4,13 +4,11 @@ import prog8.ast.IFunctionCall
 import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.expressions.*
-import prog8.ast.statements.AssignTarget
+import prog8.ast.statements.RegisterOrStatusflag
 import prog8.ast.statements.Subroutine
 import prog8.ast.statements.SubroutineParameter
 import prog8.compiler.AssemblyError
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_HI_HEX
-import prog8.compiler.target.c64.C64MachineDefinition.ESTACK_LO_HEX
-import prog8.compiler.toHex
+import prog8.compiler.target.c64.codegen.assignment.*


 internal class FunctionCallAsmGen(private val program: Program, private val asmgen: AsmGen) {
@@ -19,212 +17,225 @@ internal class FunctionCallAsmGen(private val program: Program, private val asmg
        // output the code to setup the parameters and perform the actual call
        // does NOT output the code to deal with the result values!
        val sub = stmt.target.targetSubroutine(program.namespace) ?: throw AssemblyError("undefined subroutine ${stmt.target}")
-        if(Register.X in sub.asmClobbers)
-            asmgen.out("  stx  c64.SCRATCH_ZPREGX")        // we only save X for now (required! is the eval stack pointer), screw A and Y...
+        val saveX = CpuRegister.X in sub.asmClobbers || sub.regXasResult() || sub.regXasParam()
+        if(saveX)
+            asmgen.saveRegister(CpuRegister.X)

-        val subName = asmgen.asmIdentifierName(stmt.target)
+        val subName = asmgen.asmSymbolName(stmt.target)
        if(stmt.args.isNotEmpty()) {
-            for(arg in sub.parameters.withIndex().zip(stmt.args)) {
-                translateFuncArguments(arg.first, arg.second, sub)
+            if(sub.asmParameterRegisters.isEmpty()) {
+                // via variables
+                for(arg in sub.parameters.withIndex().zip(stmt.args)) {
+                    argumentViaVariable(sub, arg.first, arg.second)
+                }
+            } else {
+                // via registers
+                if(sub.parameters.size==1) {
+                    // just a single parameter, no risk of clobbering registers
+                    argumentViaRegister(sub, sub.parameters.withIndex().single(), stmt.args[0])
+                } else {
+                    // multiple register arguments, risk of register clobbering.
+                    // evaluate arguments onto the stack, and load the registers from the evaluated values on the stack.
+                    when {
+                        stmt.args.all {it is AddressOf ||
+                                it is NumericLiteralValue ||
+                                it is StringLiteralValue ||
+                                it is ArrayLiteralValue ||
+                                it is IdentifierReference} -> {
+                            // no risk of clobbering for these simple argument types. Optimize the register loading.
+                            for(arg in sub.parameters.withIndex().zip(stmt.args)) {
+                                argumentViaRegister(sub, arg.first, arg.second)
+                            }
+                        }
+                        else -> {
+                            // Risk of clobbering due to complex expression args. Work via the stack.
+                            registerArgsViaStackEvaluation(stmt, sub)
+                        }
+                    }
+                }
            }
        }
        asmgen.out("  jsr  $subName")

-        if(Register.X in sub.asmClobbers)
-            asmgen.out("  ldx  c64.SCRATCH_ZPREGX")        // restore X again
+        if(saveX)
+            asmgen.restoreRegister(CpuRegister.X)
    }

-    private fun translateFuncArguments(parameter: IndexedValue<SubroutineParameter>, value: Expression, sub: Subroutine) {
-        val sourceIDt = value.inferType(program)
-        if(!sourceIDt.isKnown)
+    private fun registerArgsViaStackEvaluation(stmt: IFunctionCall, sub: Subroutine) {
+        // this is called when one or more of the arguments are 'complex' and
+        // cannot be assigned to a register easily or risk clobbering other registers.
+
+        if(sub.parameters.isEmpty())
+            return
+
+        // 1. load all arguments reversed onto the stack: first arg goes last (is on top).
+        for (arg in stmt.args.reversed())
+            asmgen.translateExpression(arg)
+
+        var argForCarry: IndexedValue<Pair<Expression, RegisterOrStatusflag>>? = null
+        var argForXregister: IndexedValue<Pair<Expression, RegisterOrStatusflag>>? = null
+        var argForAregister: IndexedValue<Pair<Expression, RegisterOrStatusflag>>? = null
+
+        asmgen.out("  inx")     // align estack pointer
+
+        for(argi in stmt.args.zip(sub.asmParameterRegisters).withIndex()) {
+            when {
+                argi.value.second.stack -> TODO("asmsub @stack parameter")
+                argi.value.second.statusflag == Statusflag.Pc -> {
+                    require(argForCarry == null)
+                    argForCarry = argi
+                }
+                argi.value.second.statusflag != null -> throw AssemblyError("can only use Carry as status flag parameter")
+                argi.value.second.registerOrPair in setOf(RegisterOrPair.X, RegisterOrPair.AX, RegisterOrPair.XY) -> {
+                    require(argForXregister==null)
+                    argForXregister = argi
+                }
+                argi.value.second.registerOrPair in setOf(RegisterOrPair.A, RegisterOrPair.AY) -> {
+                    require(argForAregister == null)
+                    argForAregister = argi
+                }
+                argi.value.second.registerOrPair == RegisterOrPair.Y -> {
+                    asmgen.out("  ldy  P8ESTACK_LO+${argi.index},x")
+                }
+                else -> throw AssemblyError("weird argument")
+            }
+        }
+
+        if(argForCarry!=null) {
+            asmgen.out("""
+                lda  P8ESTACK_LO+${argForCarry.index},x
+                beq  +
+                sec
+                bcs  ++
+               clc
+               php""")             // push the status flags
+        }
+
+        if(argForAregister!=null) {
+            when(argForAregister.value.second.registerOrPair) {
+                RegisterOrPair.A -> asmgen.out("  lda  P8ESTACK_LO+${argForAregister.index},x")
+                RegisterOrPair.AY -> asmgen.out("  lda  P8ESTACK_LO+${argForAregister.index},x |  ldy  P8ESTACK_HI+${argForAregister.index},x")
+                else -> throw AssemblyError("weird arg")
+            }
+        }
+
+        if(argForXregister!=null) {
+
+            if(argForAregister!=null)
+                asmgen.out("  pha")
+            when(argForXregister.value.second.registerOrPair) {
+                RegisterOrPair.X -> asmgen.out("  lda  P8ESTACK_LO+${argForXregister.index},x |  tax")
+                RegisterOrPair.AX -> asmgen.out("  ldy  P8ESTACK_LO+${argForXregister.index},x |  lda  P8ESTACK_HI+${argForXregister.index},x |  tax |  tya")
+                RegisterOrPair.XY -> asmgen.out("  ldy  P8ESTACK_HI+${argForXregister.index},x |  lda  P8ESTACK_LO+${argForXregister.index},x |  tax")
+                else -> throw AssemblyError("weird arg")
+            }
+            if(argForAregister!=null)
+                asmgen.out("  pla")
+        } else {
+            repeat(sub.parameters.size - 1) { asmgen.out("  inx") }       // unwind stack
+        }
+
+        if(argForCarry!=null)
+            asmgen.out("  plp")       // set the carry flag back to correct value
+    }
+
+    private fun argumentViaVariable(sub: Subroutine, parameter: IndexedValue<SubroutineParameter>, value: Expression) {
+        // pass parameter via a regular variable (not via registers)
+        val valueIDt = value.inferType(program)
+        if(!valueIDt.isKnown)
            throw AssemblyError("arg type unknown")
-        val sourceDt = sourceIDt.typeOrElse(DataType.STRUCT)
-        if(!argumentTypeCompatible(sourceDt, parameter.value.type))
+        val valueDt = valueIDt.typeOrElse(DataType.STRUCT)
+        if(!isArgumentTypeCompatible(valueDt, parameter.value.type))
            throw AssemblyError("argument type incompatible")
-        if(sub.asmParameterRegisters.isEmpty()) {
-            // pass parameter via a variable
-            val paramVar = parameter.value
-            val scopedParamVar = (sub.scopedname+"."+paramVar.name).split(".")
-            val target = AssignTarget(null, IdentifierReference(scopedParamVar, sub.position), null, null, sub.position)
-            target.linkParents(value.parent)
-            when (value) {
-                is NumericLiteralValue -> {
-                    // optimize when the argument is a constant literal
-                    when(parameter.value.type) {
-                        in ByteDatatypes -> asmgen.assignFromByteConstant(target, value.number.toShort())
-                        in WordDatatypes -> asmgen.assignFromWordConstant(target, value.number.toInt())
-                        DataType.FLOAT -> asmgen.assignFromFloatConstant(target, value.number.toDouble())
-                        in PassByReferenceDatatypes -> throw AssemblyError("can't pass string/array as arguments?")
-                        else -> throw AssemblyError("weird parameter datatype")
-                    }
-                }
-                is IdentifierReference -> {
-                    // optimize when the argument is a variable
-                    when (parameter.value.type) {
-                        in ByteDatatypes -> asmgen.assignFromByteVariable(target, value)
-                        in WordDatatypes -> asmgen.assignFromWordVariable(target, value)
-                        DataType.FLOAT -> asmgen.assignFromFloatVariable(target, value)
-                        in PassByReferenceDatatypes -> throw AssemblyError("can't pass string/array as arguments?")
-                        else -> throw AssemblyError("weird parameter datatype")
-                    }
-                }
-                is RegisterExpr -> {
-                    asmgen.assignFromRegister(target, value.register)
-                }
-                is DirectMemoryRead -> {
-                    when(value.addressExpression) {
+
+        val scopedParamVar = (sub.scopedname+"."+parameter.value.name).split(".")
+        val identifier = IdentifierReference(scopedParamVar, sub.position)
+        identifier.linkParents(value.parent)
+        val tgt = AsmAssignTarget(TargetStorageKind.VARIABLE, program, asmgen, parameter.value.type, variable = identifier)
+        val source = AsmAssignSource.fromAstSource(value, program).adjustDataTypeToTarget(tgt)
+        val asgn = AsmAssignment(source, tgt, false, Position.DUMMY)
+        asmgen.translateNormalAssignment(asgn)
+    }
+
+    private fun argumentViaRegister(sub: Subroutine, parameter: IndexedValue<SubroutineParameter>, value: Expression) {
+        // pass argument via a register parameter
+        val valueIDt = value.inferType(program)
+        if(!valueIDt.isKnown)
+            throw AssemblyError("arg type unknown")
+        val valueDt = valueIDt.typeOrElse(DataType.STRUCT)
+        if(!isArgumentTypeCompatible(valueDt, parameter.value.type))
+            throw AssemblyError("argument type incompatible")
+
+        val paramRegister = sub.asmParameterRegisters[parameter.index]
+        val statusflag = paramRegister.statusflag
+        val register = paramRegister.registerOrPair
+        val stack = paramRegister.stack
+        when {
+            stack -> {
+                // push arg onto the stack
+                // note: argument order is reversed (first argument will be deepest on the stack)
+                asmgen.translateExpression(value)
+            }
+            statusflag!=null -> {
+                if (statusflag == Statusflag.Pc) {
+                    // this param needs to be set last, right before the jsr
+                    // for now, this is already enforced on the subroutine definition by the Ast Checker
+                    when(value) {
                        is NumericLiteralValue -> {
-                            val address = (value.addressExpression as NumericLiteralValue).number.toInt()
-                            asmgen.assignFromMemoryByte(target, address, null)
+                            val carrySet = value.number.toInt() != 0
+                            asmgen.out(if(carrySet) "  sec" else "  clc")
                        }
                        is IdentifierReference -> {
-                            asmgen.assignFromMemoryByte(target, null, value.addressExpression as IdentifierReference)
-                        }
-                        else -> {
-                            asmgen.translateExpression(value.addressExpression)
-                            asmgen.out("  jsr  prog8_lib.read_byte_from_address |  inx")
-                            asmgen.assignFromRegister(target, Register.A)
-                        }
-                    }
-                }
-                else -> {
-                    asmgen.translateExpression(value)
-                    asmgen.assignFromEvalResult(target)
-                }
-            }
-        } else {
-            // pass parameter via a register parameter
-            val paramRegister = sub.asmParameterRegisters[parameter.index]
-            val statusflag = paramRegister.statusflag
-            val register = paramRegister.registerOrPair
-            val stack = paramRegister.stack
-            when {
-                stack -> {
-                    // push arg onto the stack
-                    // note: argument order is reversed (first argument will be deepest on the stack)
-                    asmgen.translateExpression(value)
-                }
-                statusflag!=null -> {
-                    if (statusflag == Statusflag.Pc) {
-                        // this param needs to be set last, right before the jsr
-                        // for now, this is already enforced on the subroutine definition by the Ast Checker
-                        when(value) {
-                            is NumericLiteralValue -> {
-                                val carrySet = value.number.toInt() != 0
-                                asmgen.out(if(carrySet) "  sec" else "  clc")
-                            }
-                            is IdentifierReference -> {
-                                val sourceName = asmgen.asmIdentifierName(value)
-                                asmgen.out("""
+                            val sourceName = asmgen.asmVariableName(value)
+                            asmgen.out("""
+            pha
            lda  $sourceName
            beq  +
            sec  
            bcs  ++
 +           clc
-+
+           pla
 """)
-                            }
-                            is RegisterExpr -> {
-                                when(value.register) {
-                                    Register.A -> asmgen.out("  cmp  #0")
-                                    Register.X -> asmgen.out("  txa")
-                                    Register.Y -> asmgen.out("  tya")
-                                }
-                                asmgen.out("""
-            beq  +
-            sec
-            bcs  ++
-+           clc
-+
-""")
-                            }
-                            else -> {
-                                asmgen.translateExpression(value)
-                                asmgen.out("""
-            inx                        
-            lda  $ESTACK_LO_HEX,x
+                        }
+                        else -> {
+                            asmgen.translateExpression(value)
+                            asmgen.out("""
+            inx
+            pha
+            lda  P8ESTACK_LO,x
            beq  +
            sec  
            bcs  ++
 +           clc
-+
+           pla
 """)
-                            }
-                        }
-                    }
-                    else throw AssemblyError("can only use Carry as status flag parameter")
-                }
-                register!=null && register.name.length==1 -> {
-                    when (value) {
-                        is NumericLiteralValue -> {
-                            val target = AssignTarget(Register.valueOf(register.name), null, null, null, sub.position)
-                            target.linkParents(value.parent)
-                            asmgen.assignFromByteConstant(target, value.number.toShort())
-                        }
-                        is IdentifierReference -> {
-                            val target = AssignTarget(Register.valueOf(register.name), null, null, null, sub.position)
-                            target.linkParents(value.parent)
-                            asmgen.assignFromByteVariable(target, value)
-                        }
-                        else -> {
-                            asmgen.translateExpression(value)
-                            when(register) {
-                                RegisterOrPair.A -> asmgen.out("  inx | lda  $ESTACK_LO_HEX,x")
-                                RegisterOrPair.X -> throw AssemblyError("can't pop into X register - use a variable instead")
-                                RegisterOrPair.Y -> asmgen.out("  inx | ldy  $ESTACK_LO_HEX,x")
-                                else -> throw AssemblyError("cannot assign to register pair")
-                            }
                        }
                    }
                }
-                register!=null && register.name.length==2 -> {
-                    // register pair as a 16-bit value (only possible for subroutine parameters)
-                    when (value) {
-                        is NumericLiteralValue -> {
-                            // optimize when the argument is a constant literal
-                            val hex = value.number.toHex()
-                            when (register) {
-                                RegisterOrPair.AX -> asmgen.out("  lda  #<$hex  |  ldx  #>$hex")
-                                RegisterOrPair.AY -> asmgen.out("  lda  #<$hex  |  ldy  #>$hex")
-                                RegisterOrPair.XY -> asmgen.out("  ldx  #<$hex  |  ldy  #>$hex")
-                                else -> {}
-                            }
-                        }
-                        is AddressOf -> {
-                            // optimize when the argument is an address of something
-                            val sourceName = asmgen.asmIdentifierName(value.identifier)
-                            when (register) {
-                                RegisterOrPair.AX -> asmgen.out("  lda  #<$sourceName  |  ldx  #>$sourceName")
-                                RegisterOrPair.AY -> asmgen.out("  lda  #<$sourceName  |  ldy  #>$sourceName")
-                                RegisterOrPair.XY -> asmgen.out("  ldx  #<$sourceName  |  ldy  #>$sourceName")
-                                else -> {}
-                            }
-                        }
-                        is IdentifierReference -> {
-                            val sourceName = asmgen.asmIdentifierName(value)
-                            when (register) {
-                                RegisterOrPair.AX -> asmgen.out("  lda  $sourceName  |  ldx  $sourceName+1")
-                                RegisterOrPair.AY -> asmgen.out("  lda  $sourceName  |  ldy  $sourceName+1")
-                                RegisterOrPair.XY -> asmgen.out("  ldx  $sourceName  |  ldy  $sourceName+1")
-                                else -> {}
-                            }
-                        }
-                        else -> {
-                            asmgen.translateExpression(value)
-                            if (register == RegisterOrPair.AX || register == RegisterOrPair.XY)
-                                throw AssemblyError("can't use X register here - use a variable")
-                            else if (register == RegisterOrPair.AY)
-                                asmgen.out("  inx |  lda  $ESTACK_LO_HEX,x  |  ldy  $ESTACK_HI_HEX,x")
-                        }
-                    }
+                else throw AssemblyError("can only use Carry as status flag parameter")
+            }
+            else -> {
+                // via register or register pair
+                val target = AsmAssignTarget.fromRegisters(register!!, program, asmgen)
+                val src = if(valueDt in PassByReferenceDatatypes) {
+                    val addr = AddressOf(value as IdentifierReference, Position.DUMMY)
+                    AsmAssignSource.fromAstSource(addr, program).adjustDataTypeToTarget(target)
+                } else {
+                    AsmAssignSource.fromAstSource(value, program).adjustDataTypeToTarget(target)
                }
+
+                asmgen.translateNormalAssignment(AsmAssignment(src, target, false, Position.DUMMY))
            }
        }
    }

-    private fun argumentTypeCompatible(argType: DataType, paramType: DataType): Boolean {
+    private fun isArgumentTypeCompatible(argType: DataType, paramType: DataType): Boolean {
        if(argType isAssignableTo paramType)
            return true
+        if(argType in ByteDatatypes && paramType in ByteDatatypes)
+            return true
+        if(argType in WordDatatypes && paramType in WordDatatypes)
+            return true

        // we have a special rule for some types.
        // strings are assignable to UWORD, for example, and vice versa
@@ -4,10 +4,8 @@ import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.expressions.IdentifierReference
 import prog8.ast.expressions.NumericLiteralValue
-import prog8.ast.expressions.RegisterExpr
 import prog8.ast.statements.PostIncrDecr
 import prog8.compiler.AssemblyError
-import prog8.compiler.target.c64.C64MachineDefinition.C64Zeropage
 import prog8.compiler.toHex


@@ -17,28 +15,10 @@ internal class PostIncrDecrAsmGen(private val program: Program, private val asmg
        val targetIdent = stmt.target.identifier
        val targetMemory = stmt.target.memoryAddress
        val targetArrayIdx = stmt.target.arrayindexed
-        val targetRegister = stmt.target.register
        when {
-            targetRegister!=null -> {
-                when(targetRegister) {
-                    Register.A -> {
-                        if(incr)
-                            asmgen.out("  clc |  adc  #1 ")
-                        else
-                            asmgen.out("  sec |  sbc  #1 ")
-                    }
-                    Register.X -> {
-                        if(incr) asmgen.out("  inx") else asmgen.out("  dex")
-                    }
-                    Register.Y -> {
-                        if(incr) asmgen.out("  iny") else asmgen.out("  dey")
-                    }
-                }
-            }
            targetIdent!=null -> {
-                val what = asmgen.asmIdentifierName(targetIdent)
-                val dt = stmt.target.inferType(program, stmt).typeOrElse(DataType.STRUCT)
-                when (dt) {
+                val what = asmgen.asmVariableName(targetIdent)
+                when (stmt.target.inferType(program, stmt).typeOrElse(DataType.STRUCT)) {
                    in ByteDatatypes -> asmgen.out(if (incr) "  inc  $what" else "  dec  $what")
                    in WordDatatypes -> {
                        if(incr)
@@ -53,7 +33,7 @@ internal class PostIncrDecrAsmGen(private val program: Program, private val asmg
                    }
                    DataType.FLOAT -> {
                        asmgen.out("  lda  #<$what |  ldy  #>$what")
-                        asmgen.out(if(incr) "  jsr  c64flt.inc_var_f" else "  jsr  c64flt.dec_var_f")
+                        asmgen.out(if(incr) "  jsr  floats.inc_var_f" else "  jsr  floats.dec_var_f")
                    }
                    else -> throw AssemblyError("need numeric type")
                }
@@ -65,86 +45,91 @@ internal class PostIncrDecrAsmGen(private val program: Program, private val asmg
                        asmgen.out(if(incr) "  inc  $what" else "  dec  $what")
                    }
                    is IdentifierReference -> {
-                        val what = asmgen.asmIdentifierName(addressExpr)
-                        asmgen.out(if(incr) "  inc  $what" else "  dec  $what")
+                        val what = asmgen.asmVariableName(addressExpr)
+                        asmgen.out("  lda  $what |  sta  (+) +1 |  lda  $what+1 |  sta  (+) +2")
+                        if(incr)
+                            asmgen.out("+\tinc  ${'$'}ffff\t; modified")
+                        else
+                            asmgen.out("+\tdec  ${'$'}ffff\t; modified")
+                    }
+                    else -> {
+                        asmgen.translateExpression(addressExpr)
+                        asmgen.out("""
+                            inx
+                            lda  P8ESTACK_LO,x
+                            sta  (+) + 1
+                            lda  P8ESTACK_HI,x
+                            sta  (+) + 2
+                        """)
+                        if(incr)
+                            asmgen.out("+\tinc  ${'$'}ffff\t; modified")
+                        else
+                            asmgen.out("+\tdec  ${'$'}ffff\t; modified")
                    }
-                    else -> throw AssemblyError("weird target type $targetMemory")
                }
            }
            targetArrayIdx!=null -> {
                val index = targetArrayIdx.arrayspec.index
-                val what = asmgen.asmIdentifierName(targetArrayIdx.identifier)
-                val arrayDt = targetArrayIdx.identifier.inferType(program).typeOrElse(DataType.STRUCT)
-                val elementDt = ArrayElementTypes.getValue(arrayDt)
+                val asmArrayvarname = asmgen.asmVariableName(targetArrayIdx.identifier)
+                val elementDt = targetArrayIdx.inferType(program).typeOrElse(DataType.STRUCT)
                when(index) {
                    is NumericLiteralValue -> {
                        val indexValue = index.number.toInt() * elementDt.memorySize()
                        when(elementDt) {
-                            in ByteDatatypes -> asmgen.out(if (incr) "  inc  $what+$indexValue" else "  dec  $what+$indexValue")
+                            in ByteDatatypes -> asmgen.out(if (incr) "  inc  $asmArrayvarname+$indexValue" else "  dec  $asmArrayvarname+$indexValue")
                            in WordDatatypes -> {
                                if(incr)
-                                    asmgen.out(" inc  $what+$indexValue |  bne  + |  inc  $what+$indexValue+1 |+")
+                                    asmgen.out(" inc  $asmArrayvarname+$indexValue |  bne  + |  inc  $asmArrayvarname+$indexValue+1 |+")
                                else
                                    asmgen.out("""
-        lda  $what+$indexValue
+        lda  $asmArrayvarname+$indexValue
        bne  +
-        dec  $what+$indexValue+1
-+       dec  $what+$indexValue 
+        dec  $asmArrayvarname+$indexValue+1
+       dec  $asmArrayvarname+$indexValue 
 """)
                            }
                            DataType.FLOAT -> {
-                                asmgen.out("  lda  #<$what+$indexValue |  ldy  #>$what+$indexValue")
-                                asmgen.out(if(incr) "  jsr  c64flt.inc_var_f" else "  jsr  c64flt.dec_var_f")
+                                asmgen.out("  lda  #<$asmArrayvarname+$indexValue |  ldy  #>$asmArrayvarname+$indexValue")
+                                asmgen.out(if(incr) "  jsr  floats.inc_var_f" else "  jsr  floats.dec_var_f")
                            }
                            else -> throw AssemblyError("need numeric type")
                        }
                    }
-                    is RegisterExpr -> {
-                        // TODO optimize common cases
-                        asmgen.translateArrayIndexIntoA(targetArrayIdx)
-                        incrDecrArrayvalueWithIndexA(incr, arrayDt, what)
-                    }
-                    is IdentifierReference -> {
-                        // TODO optimize common cases
-                        asmgen.translateArrayIndexIntoA(targetArrayIdx)
-                        incrDecrArrayvalueWithIndexA(incr, arrayDt, what)
-                    }
                    else -> {
-                        // TODO optimize common cases
-                        asmgen.translateArrayIndexIntoA(targetArrayIdx)
-                        incrDecrArrayvalueWithIndexA(incr, arrayDt, what)
+                        asmgen.loadScaledArrayIndexIntoRegister(targetArrayIdx, elementDt, CpuRegister.A)
+                        asmgen.saveRegister(CpuRegister.X)
+                        asmgen.out("  tax")
+                        when(elementDt) {
+                            in ByteDatatypes -> {
+                                asmgen.out(if(incr) "  inc  $asmArrayvarname,x" else "  dec  $asmArrayvarname,x")
+                            }
+                            in WordDatatypes -> {
+                                if(incr)
+                                    asmgen.out(" inc  $asmArrayvarname,x |  bne  + |  inc  $asmArrayvarname+1,x |+")
+                                else
+                                    asmgen.out("""
+        lda  $asmArrayvarname,x
+        bne  +
+        dec  $asmArrayvarname+1,x
+       dec  $asmArrayvarname 
+""")
+                            }
+                            DataType.FLOAT -> {
+                                asmgen.out("""
+                        ldy  #>$asmArrayvarname
+                        clc
+                        adc  #<$asmArrayvarname
+                        bcc  +
+                        iny
+                       jsr  floats.inc_var_f""")
+                            }
+                            else -> throw AssemblyError("weird array elt dt")
+                        }
+                        asmgen.restoreRegister(CpuRegister.X)
                    }
                }
            }
            else -> throw AssemblyError("weird target type ${stmt.target}")
        }
    }
-
-    private fun incrDecrArrayvalueWithIndexA(incr: Boolean, arrayDt: DataType, arrayVarName: String) {
-        asmgen.out("  stx  ${C64Zeropage.SCRATCH_REG_X} |  tax")
-        when(arrayDt) {
-            DataType.STR,
-            DataType.ARRAY_UB, DataType.ARRAY_B -> {
-                asmgen.out(if(incr) "  inc  $arrayVarName,x" else "  dec  $arrayVarName,x")
-            }
-            DataType.ARRAY_UW, DataType.ARRAY_W -> {
-                if(incr)
-                    asmgen.out(" inc  $arrayVarName,x |  bne  + |  inc  $arrayVarName+1,x |+")
-                else
-                    asmgen.out("""
-        lda  $arrayVarName,x
-        bne  +
-        dec  $arrayVarName+1,x
-+       dec  $arrayVarName 
-""")
-            }
-            DataType.ARRAY_F -> {
-                asmgen.out("  lda  #<$arrayVarName |  ldy  #>$arrayVarName")
-                asmgen.out(if(incr) "  jsr  c64flt.inc_indexed_var_f" else "  jsr  c64flt.dec_indexed_var_f")
-            }
-            else -> throw AssemblyError("weird array dt")
-        }
-        asmgen.out("  ldx  ${C64Zeropage.SCRATCH_REG_X}")
-    }
-
 }
@@ -0,0 +1,165 @@
+package prog8.compiler.target.c64.codegen.assignment
+
+import prog8.ast.Program
+import prog8.ast.base.*
+import prog8.ast.expressions.*
+import prog8.ast.statements.AssignTarget
+import prog8.ast.statements.Assignment
+import prog8.ast.statements.DirectMemoryWrite
+import prog8.compiler.AssemblyError
+import prog8.compiler.target.c64.codegen.AsmGen
+
+
+internal enum class TargetStorageKind {
+    VARIABLE,
+    ARRAY,
+    MEMORY,
+    REGISTER,
+    STACK
+}
+
+internal enum class SourceStorageKind {
+    LITERALNUMBER,
+    VARIABLE,
+    ARRAY,
+    MEMORY,
+    REGISTER,
+    STACK,              // value is already present on stack
+    EXPRESSION,         // expression in ast-form, still to be evaluated
+}
+
+internal class AsmAssignTarget(val kind: TargetStorageKind,
+                               program: Program,
+                               asmgen: AsmGen,
+                               val datatype: DataType,
+                               val variable: IdentifierReference? = null,
+                               val array: ArrayIndexedExpression? = null,
+                               val memory: DirectMemoryWrite? = null,
+                               val register: RegisterOrPair? = null,
+                               val origAstTarget: AssignTarget? = null
+                               )
+{
+    val constMemoryAddress by lazy { memory?.addressExpression?.constValue(program)?.number?.toInt() ?: 0}
+    val constArrayIndexValue by lazy { array?.arrayspec?.constIndex() }
+    val vardecl by lazy { variable?.targetVarDecl(program.namespace)!! }
+    val asmVarname by lazy {
+        if(variable!=null)
+            asmgen.asmVariableName(variable)
+        else
+            asmgen.asmVariableName(array!!.identifier)
+    }
+
+    lateinit var origAssign: AsmAssignment
+
+    init {
+        if(variable!=null && vardecl.type == VarDeclType.CONST)
+            throw AssemblyError("can't assign to a constant")
+        if(register!=null && datatype !in IntegerDatatypes)
+            throw AssemblyError("register must be integer type")
+    }
+
+    companion object {
+        fun fromAstAssignment(assign: Assignment, program: Program, asmgen: AsmGen): AsmAssignTarget = with(assign.target) {
+            val dt = inferType(program, assign).typeOrElse(DataType.STRUCT)
+            when {
+                identifier != null -> AsmAssignTarget(TargetStorageKind.VARIABLE, program, asmgen, dt, variable=identifier, origAstTarget =  this)
+                arrayindexed != null -> AsmAssignTarget(TargetStorageKind.ARRAY, program, asmgen, dt, array = arrayindexed, origAstTarget =  this)
+                memoryAddress != null -> AsmAssignTarget(TargetStorageKind.MEMORY, program, asmgen, dt, memory =  memoryAddress, origAstTarget =  this)
+                else -> throw AssemblyError("weird target")
+            }
+        }
+
+        fun fromRegisters(registers: RegisterOrPair, program: Program, asmgen: AsmGen): AsmAssignTarget =
+                when(registers) {
+                    RegisterOrPair.A,
+                    RegisterOrPair.X,
+                    RegisterOrPair.Y -> AsmAssignTarget(TargetStorageKind.REGISTER, program, asmgen, DataType.UBYTE, register = registers)
+                    RegisterOrPair.AX,
+                    RegisterOrPair.AY,
+                    RegisterOrPair.XY -> AsmAssignTarget(TargetStorageKind.REGISTER, program, asmgen, DataType.UWORD, register = registers)
+                }
+    }
+}
+
+internal class AsmAssignSource(val kind: SourceStorageKind,
+                               private val program: Program,
+                               val datatype: DataType,
+                               val variable: IdentifierReference? = null,
+                               val array: ArrayIndexedExpression? = null,
+                               val memory: DirectMemoryRead? = null,
+                               val register: CpuRegister? = null,
+                               val number: NumericLiteralValue? = null,
+                               val expression: Expression? = null
+)
+{
+    val constMemoryAddress by lazy { memory?.addressExpression?.constValue(program)?.number?.toInt() ?: 0}
+    val constArrayIndexValue by lazy { array?.arrayspec?.constIndex() }
+    val vardecl by lazy { variable?.targetVarDecl(program.namespace)!! }
+
+    companion object {
+        fun fromAstSource(value: Expression, program: Program): AsmAssignSource {
+            val cv = value.constValue(program)
+            if(cv!=null)
+                return AsmAssignSource(SourceStorageKind.LITERALNUMBER, program, cv.type, number = cv)
+
+            return when(value) {
+                is NumericLiteralValue -> AsmAssignSource(SourceStorageKind.LITERALNUMBER, program, value.type, number = cv)
+                is StringLiteralValue -> throw AssemblyError("string literal value should not occur anymore for asm generation")
+                is ArrayLiteralValue -> throw AssemblyError("array literal value should not occur anymore for asm generation")
+                is IdentifierReference -> {
+                    val dt = value.inferType(program).typeOrElse(DataType.STRUCT)
+                    AsmAssignSource(SourceStorageKind.VARIABLE, program, dt, variable = value)
+                }
+                is DirectMemoryRead -> {
+                    AsmAssignSource(SourceStorageKind.MEMORY, program, DataType.UBYTE, memory = value)
+                }
+                is ArrayIndexedExpression -> {
+                    val dt = value.inferType(program).typeOrElse(DataType.STRUCT)
+                    AsmAssignSource(SourceStorageKind.ARRAY, program, dt, array = value)
+                }
+                else -> {
+                    val dt = value.inferType(program).typeOrElse(DataType.STRUCT)
+                    AsmAssignSource(SourceStorageKind.EXPRESSION, program, dt, expression = value)
+                }
+            }
+        }
+    }
+
+    fun getAstValue(): Expression = when(kind) {
+        SourceStorageKind.LITERALNUMBER -> number!!
+        SourceStorageKind.VARIABLE -> variable!!
+        SourceStorageKind.ARRAY -> array!!
+        SourceStorageKind.MEMORY -> memory!!
+        SourceStorageKind.EXPRESSION -> expression!!
+        SourceStorageKind.REGISTER -> throw AssemblyError("cannot get a register source as Ast node")
+        SourceStorageKind.STACK -> throw AssemblyError("cannot get a stack source as Ast node")
+    }
+
+    fun withAdjustedDt(newType: DataType) =
+            AsmAssignSource(kind, program, newType, variable, array, memory, register, number, expression)
+
+    fun adjustDataTypeToTarget(target: AsmAssignTarget): AsmAssignSource {
+        // allow some signed/unsigned relaxations
+        if(target.datatype!=datatype) {
+            if(target.datatype in ByteDatatypes && datatype in ByteDatatypes) {
+                return withAdjustedDt(target.datatype)
+            } else if(target.datatype in WordDatatypes && datatype in WordDatatypes) {
+                return withAdjustedDt(target.datatype)
+            }
+        }
+        return this
+    }
+
+}
+
+
+internal class AsmAssignment(val source: AsmAssignSource,
+                             val target: AsmAssignTarget,
+                             val isAugmentable: Boolean,
+                             val position: Position) {
+
+    init {
+        if(target.register !in setOf(RegisterOrPair.XY, RegisterOrPair.AX, RegisterOrPair.AY))
+            require(source.datatype.memorySize() == target.datatype.memorySize()) { "source and target datatype must be same storage class" }
+    }
+}
@@ -0,0 +1,123 @@
+package prog8.compiler.target.cx16
+
+import prog8.ast.Program
+import prog8.compiler.*
+import prog8.compiler.target.CpuType
+import prog8.compiler.target.IMachineDefinition
+import prog8.compiler.target.c64.C64MachineDefinition
+import prog8.parser.ModuleImporter
+import java.io.IOException
+
+internal object CX16MachineDefinition: IMachineDefinition {
+
+    override val cpu = CpuType.CPU65c02
+
+    // 5-byte cbm MFLPT format limitations:
+    override val FLOAT_MAX_POSITIVE = 1.7014118345e+38         // bytes: 255,127,255,255,255
+    override val FLOAT_MAX_NEGATIVE = -1.7014118345e+38        // bytes: 255,255,255,255,255
+    override val FLOAT_MEM_SIZE = 5
+    override val POINTER_MEM_SIZE = 2
+    override val BASIC_LOAD_ADDRESS = 0x0801
+    override val RAW_LOAD_ADDRESS = 0x8000
+
+    // the 2*256 byte evaluation stack (on which bytes, words, and even floats are stored during calculations)
+    // and some heavily used string constants derived from the two values above
+    override val ESTACK_LO = 0x0400        //  $0400-$04ff inclusive
+    override val ESTACK_HI = 0x0500        //  $0500-$05ff inclusive
+
+    override lateinit var zeropage: Zeropage
+
+    override fun getFloat(num: Number) = C64MachineDefinition.Mflpt5.fromNumber(num)
+
+    override fun getFloatRomConst(number: Double): String? = null       // Cx16 has no pulblic ROM float locations
+    override fun importLibs(compilerOptions: CompilationOptions, importer: ModuleImporter, program: Program) {
+        if (compilerOptions.launcher == LauncherType.BASIC || compilerOptions.output == OutputType.PRG)
+            importer.importLibraryModule(program, "syslib")
+    }
+
+    override fun launchEmulator(programName: String) {
+        for(emulator in listOf("x16emu")) {
+            println("\nStarting Commander X16 emulator $emulator...")
+            val cmdline = listOf(emulator, "-rom", "/usr/share/x16-rom/rom.bin", "-scale", "2",
+                    "-run", "-prg", programName + ".prg")
+            val processb = ProcessBuilder(cmdline).inheritIO()
+            val process: Process
+            try {
+                process=processb.start()
+            } catch(x: IOException) {
+                continue  // try the next emulator executable
+            }
+            process.waitFor()
+            break
+        }
+    }
+
+    override fun initializeZeropage(compilerOptions: CompilationOptions) {
+        zeropage = CX16Zeropage(compilerOptions)
+    }
+
+    // 6502 opcodes (including aliases and illegal opcodes), these cannot be used as variable or label names
+    override val opcodeNames = setOf("adc", "and", "asl", "bcc", "bcs",
+            "beq", "bge", "bit", "blt", "bmi", "bne", "bpl", "brk", "bvc", "bvs", "clc",
+            "cld", "cli", "clv", "cmp", "cpx", "cpy", "dec", "dex", "dey",
+            "eor", "gcc", "gcs", "geq", "gge", "glt", "gmi", "gne", "gpl", "gvc", "gvs",
+            "inc", "inx", "iny", "jmp", "jsr",
+            "lda", "ldx", "ldy", "lsr", "nop", "ora", "pha", "php",
+            "pla", "plp", "rol", "ror", "rti", "rts", "sbc",
+            "sec", "sed", "sei",
+            "sta", "stx", "sty", "tax", "tay", "tsx", "txa", "txs", "tya",
+            "bra", "phx", "phy", "plx", "ply", "stz", "trb", "tsb", "bbr", "bbs",
+            "rmb", "smb", "stp", "wai")
+
+
+    internal class CX16Zeropage(options: CompilationOptions) : Zeropage(options) {
+
+        override val SCRATCH_B1 = 0x79      // temp storage for a single byte
+        override val SCRATCH_REG = 0x7a     // temp storage for a register
+        override val SCRATCH_W1 = 0x7c      // temp storage 1 for a word  $7c+$7d
+        override val SCRATCH_W2 = 0x7e      // temp storage 2 for a word  $7e+$7f
+
+
+        override val exitProgramStrategy: ExitProgramStrategy = when (options.zeropage) {
+            ZeropageType.BASICSAFE, ZeropageType.DONTUSE -> ExitProgramStrategy.CLEAN_EXIT
+            ZeropageType.KERNALSAFE, ZeropageType.FULL -> ExitProgramStrategy.SYSTEM_RESET
+            else -> ExitProgramStrategy.SYSTEM_RESET
+        }
+
+
+        init {
+            if (options.floats && options.zeropage !in setOf(ZeropageType.BASICSAFE, ZeropageType.DONTUSE ))
+                throw CompilerException("when floats are enabled, zero page type should be 'basicsafe' or 'dontuse'")
+
+            // the addresses 0x02 to 0x21 (inclusive) are taken for sixteen virtual 16-bit api registers.
+
+            when (options.zeropage) {
+                ZeropageType.FULL -> {
+                    free.addAll(0x22..0xff)
+                    free.removeAll(listOf(SCRATCH_B1, SCRATCH_REG, SCRATCH_W1, SCRATCH_W1 + 1, SCRATCH_W2, SCRATCH_W2 + 1))
+                }
+                ZeropageType.KERNALSAFE -> {
+                    free.addAll(0x22..0x7f)
+                    free.addAll(0xa9..0xff)
+                    free.removeAll(listOf(SCRATCH_B1, SCRATCH_REG, SCRATCH_W1, SCRATCH_W1 + 1, SCRATCH_W2, SCRATCH_W2 + 1))
+                }
+                ZeropageType.BASICSAFE -> {
+                    free.addAll(0x22..0x7f)
+                    free.removeAll(listOf(SCRATCH_B1, SCRATCH_REG, SCRATCH_W1, SCRATCH_W1 + 1, SCRATCH_W2, SCRATCH_W2 + 1))
+                }
+                ZeropageType.DONTUSE -> {
+                    free.clear() // don't use zeropage at all
+                }
+                else -> throw CompilerException("for this machine target, zero page type 'floatsafe' is not available. ${options.zeropage}")
+            }
+
+            require(SCRATCH_B1 !in free)
+            require(SCRATCH_REG !in free)
+            require(SCRATCH_W1 !in free)
+            require(SCRATCH_W2 !in free)
+
+            for (reserved in options.zpReserved)
+                reserve(reserved)
+        }
+    }
+}
@@ -3,6 +3,8 @@ package prog8.functions
 import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.expressions.*
+import prog8.ast.statements.StructDecl
+import prog8.ast.statements.VarDecl
 import prog8.compiler.CompilerException
 import kotlin.math.*

@@ -25,8 +27,6 @@ val BuiltinFunctions = mapOf(
    "ror"         to FSignature(false, listOf(FParam("item", setOf(DataType.UBYTE, DataType.UWORD))), null),
    "rol2"        to FSignature(false, listOf(FParam("item", setOf(DataType.UBYTE, DataType.UWORD))), null),
    "ror2"        to FSignature(false, listOf(FParam("item", setOf(DataType.UBYTE, DataType.UWORD))), null),
-    "lsl"         to FSignature(false, listOf(FParam("item", IntegerDatatypes)), null),
-    "lsr"         to FSignature(false, listOf(FParam("item", IntegerDatatypes)), null),
    "sort"        to FSignature(false, listOf(FParam("array", ArrayDatatypes)), null),
    "reverse"     to FSignature(false, listOf(FParam("array", ArrayDatatypes)), null),
        // these few have a return value depending on the argument(s):
@@ -35,6 +35,7 @@ val BuiltinFunctions = mapOf(
    "sum"         to FSignature(true, listOf(FParam("values", ArrayDatatypes)), null) { a, p, prg -> collectionArg(a, p, prg, ::builtinSum) },      // type depends on args
    "abs"         to FSignature(true, listOf(FParam("value", NumericDatatypes)), null, ::builtinAbs),      // type depends on argument
    "len"         to FSignature(true, listOf(FParam("values", IterableDatatypes)), null, ::builtinLen),    // type is UBYTE or UWORD depending on actual length
+    "sizeof"      to FSignature(true, listOf(FParam("object", DataType.values().toSet())), DataType.UBYTE, ::builtinSizeof),
        // normal functions follow:
    "sgn"         to FSignature(true, listOf(FParam("value", NumericDatatypes)), DataType.BYTE, ::builtinSgn ),
    "sin"         to FSignature(true, listOf(FParam("rads", setOf(DataType.FLOAT))), DataType.FLOAT) { a, p, prg -> oneDoubleArg(a, p, prg, Math::sin) },
@@ -62,7 +63,7 @@ val BuiltinFunctions = mapOf(
    "all"         to FSignature(true, listOf(FParam("values", ArrayDatatypes)), DataType.UBYTE) { a, p, prg -> collectionArg(a, p, prg, ::builtinAll) },
    "lsb"         to FSignature(true, listOf(FParam("value", setOf(DataType.UWORD, DataType.WORD))), DataType.UBYTE) { a, p, prg -> oneIntArgOutputInt(a, p, prg) { x: Int -> x and 255 }},
    "msb"         to FSignature(true, listOf(FParam("value", setOf(DataType.UWORD, DataType.WORD))), DataType.UBYTE) { a, p, prg -> oneIntArgOutputInt(a, p, prg) { x: Int -> x ushr 8 and 255}},
-    "mkword"      to FSignature(true, listOf(FParam("lsb", setOf(DataType.UBYTE)), FParam("msb", setOf(DataType.UBYTE))), DataType.UWORD, ::builtinMkword),
+    "mkword"      to FSignature(true, listOf(FParam("msb", setOf(DataType.UBYTE)), FParam("lsb", setOf(DataType.UBYTE))), DataType.UWORD, ::builtinMkword),
    "rnd"         to FSignature(true, emptyList(), DataType.UBYTE),
    "rndw"        to FSignature(true, emptyList(), DataType.UWORD),
    "rndf"        to FSignature(true, emptyList(), DataType.FLOAT),
@@ -87,12 +88,25 @@ val BuiltinFunctions = mapOf(
                            FParam("address", IterableDatatypes + DataType.UWORD),
                            FParam("numwords", setOf(DataType.UWORD)),
                            FParam("wordvalue", setOf(DataType.UWORD, DataType.WORD))), null),
-    "strlen"      to FSignature(true, listOf(FParam("string", setOf(DataType.STR))), DataType.UBYTE, ::builtinStrlen)
+    "strlen"      to FSignature(true, listOf(FParam("string", setOf(DataType.STR))), DataType.UBYTE, ::builtinStrlen),
+    "substr"      to FSignature(false, listOf(
+            FParam("source", IterableDatatypes + DataType.UWORD),
+            FParam("target", IterableDatatypes + DataType.UWORD),
+            FParam("start", setOf(DataType.UBYTE)),
+            FParam("length", setOf(DataType.UBYTE))), null),
+    "leftstr"      to FSignature(false, listOf(
+            FParam("source", IterableDatatypes + DataType.UWORD),
+            FParam("target", IterableDatatypes + DataType.UWORD),
+            FParam("length", setOf(DataType.UBYTE))), null),
+    "rightstr"      to FSignature(false, listOf(
+            FParam("source", IterableDatatypes + DataType.UWORD),
+            FParam("target", IterableDatatypes + DataType.UWORD),
+            FParam("length", setOf(DataType.UBYTE))), null)
 )

-fun builtinMax(array: List<Number>): Number = array.maxBy { it.toDouble() }!!
+fun builtinMax(array: List<Number>): Number = array.maxByOrNull { it.toDouble() }!!

-fun builtinMin(array: List<Number>): Number = array.minBy { it.toDouble() }!!
+fun builtinMin(array: List<Number>): Number = array.minByOrNull { it.toDouble() }!!

 fun builtinSum(array: List<Number>): Number = array.sumByDouble { it.toDouble() }

@@ -172,6 +186,7 @@ fun builtinFunctionReturnType(function: String, args: List<Expression>, program:


 class NotConstArgumentException: AstException("not a const argument to a built-in function")
+class CannotEvaluateException(func:String, msg: String): FatalAstException("cannot evaluate built-in function $func: $msg")


 private fun oneDoubleArg(args: List<Expression>, position: Position, program: Program, function: (arg: Double)->Number): NumericLiteralValue {
@@ -226,54 +241,88 @@ private fun builtinAbs(args: List<Expression>, position: Position, program: Prog
    }
 }

+private fun builtinSizeof(args: List<Expression>, position: Position, program: Program): NumericLiteralValue {
+    // 1 arg, type = anything, result type = ubyte
+    if(args.size!=1)
+        throw SyntaxError("sizeof requires one argument", position)
+    if(args[0] !is IdentifierReference)
+        throw SyntaxError("sizeof argument should be an identifier", position)
+
+    val dt = args[0].inferType(program)
+    if(dt.isKnown) {
+        val target = (args[0] as IdentifierReference).targetStatement(program.namespace)
+                ?: throw CannotEvaluateException("sizeof", "no target")
+
+        fun structSize(target: StructDecl) =
+                NumericLiteralValue(DataType.UBYTE, target.statements.map { (it as VarDecl).datatype.memorySize() }.sum(), position)
+
+        return when {
+            dt.typeOrElse(DataType.STRUCT) in ArrayDatatypes -> {
+                val length = (target as VarDecl).arraysize!!.constIndex() ?: throw CannotEvaluateException("sizeof", "unknown array size")
+                val elementDt = ArrayElementTypes.getValue(dt.typeOrElse(DataType.STRUCT))
+                numericLiteral(elementDt.memorySize() * length, position)
+            }
+            dt.istype(DataType.STRUCT) -> {
+                when (target) {
+                    is VarDecl -> structSize(target.struct!!)
+                    is StructDecl -> structSize(target)
+                    else -> throw CompilerException("weird struct type $target")
+                }
+            }
+            dt.istype(DataType.STR) -> throw SyntaxError("sizeof str is undefined, did you mean len?", position)
+            else -> NumericLiteralValue(DataType.UBYTE, dt.typeOrElse(DataType.STRUCT).memorySize(), position)
+        }
+    } else {
+        throw SyntaxError("sizeof invalid argument type", position)
+    }
+}
+
 private fun builtinStrlen(args: List<Expression>, position: Position, program: Program): NumericLiteralValue {
    if (args.size != 1)
        throw SyntaxError("strlen requires one argument", position)
-    val argument = args[0].constValue(program) ?: throw NotConstArgumentException()
-    if(argument.type != DataType.STR)
-        throw SyntaxError("strlen must have string argument", position)
-
-    throw NotConstArgumentException()       // this function is not considering the string argument a constant
+    val argument=args[0]
+    if(argument is StringLiteralValue)
+        return NumericLiteralValue.optimalInteger(argument.value.length, argument.position)
+    val vardecl = (argument as IdentifierReference).targetVarDecl(program.namespace)
+    if(vardecl!=null) {
+        if(vardecl.datatype!=DataType.STR)
+            throw SyntaxError("strlen must have string argument", position)
+        if(vardecl.autogeneratedDontRemove) {
+            return NumericLiteralValue.optimalInteger((vardecl.value as StringLiteralValue).value.length, argument.position)
+        }
+    }
+    throw NotConstArgumentException()
 }

 private fun builtinLen(args: List<Expression>, position: Position, program: Program): NumericLiteralValue {
    // note: in some cases the length is > 255 and then we have to return a UWORD type instead of a UBYTE.
    if(args.size!=1)
        throw SyntaxError("len requires one argument", position)
-    val constArg = args[0].constValue(program)
-    if(constArg!=null)
-        throw SyntaxError("len of weird argument ${args[0]}", position)

    val directMemVar = ((args[0] as? DirectMemoryRead)?.addressExpression as? IdentifierReference)?.targetVarDecl(program.namespace)
-    var arraySize = directMemVar?.arraysize?.size()
+    var arraySize = directMemVar?.arraysize?.constIndex()
    if(arraySize != null)
        return NumericLiteralValue.optimalInteger(arraySize, position)
    if(args[0] is ArrayLiteralValue)
        return NumericLiteralValue.optimalInteger((args[0] as ArrayLiteralValue).value.size, position)
    if(args[0] !is IdentifierReference)
-        throw SyntaxError("len argument should be an identifier, but is ${args[0]}", position)
-    val target = (args[0] as IdentifierReference).targetVarDecl(program.namespace)!!
+        throw SyntaxError("len argument should be an identifier", position)
+    val target = (args[0] as IdentifierReference).targetVarDecl(program.namespace)
+            ?: throw CannotEvaluateException("len", "no target vardecl")

    return when(target.datatype) {
-        DataType.ARRAY_UB, DataType.ARRAY_B, DataType.ARRAY_UW, DataType.ARRAY_W -> {
-            arraySize = target.arraysize!!.size()!!
-            if(arraySize>256)
-                throw CompilerException("array length exceeds byte limit ${target.position}")
-            NumericLiteralValue.optimalInteger(arraySize, args[0].position)
-        }
-        DataType.ARRAY_F -> {
-            arraySize = target.arraysize!!.size()!!
-            if(arraySize>256)
-                throw CompilerException("array length exceeds byte limit ${target.position}")
+        DataType.ARRAY_UB, DataType.ARRAY_B, DataType.ARRAY_UW, DataType.ARRAY_W, DataType.ARRAY_F -> {
+            arraySize = target.arraysize?.constIndex()
+            if(arraySize==null)
+                throw CannotEvaluateException("len", "arraysize unknown")
            NumericLiteralValue.optimalInteger(arraySize, args[0].position)
        }
        DataType.STR -> {
            val refLv = target.value as StringLiteralValue
-            if(refLv.value.length>255)
-                throw CompilerException("string length exceeds byte limit ${refLv.position}")
            NumericLiteralValue.optimalInteger(refLv.value.length, args[0].position)
        }
-        in NumericDatatypes -> throw SyntaxError("len of weird argument ${args[0]}", position)
+        DataType.STRUCT -> throw SyntaxError("cannot use len on struct, did you mean sizeof?", args[0].position)
+        in NumericDatatypes -> throw SyntaxError("cannot use len on numeric value, did you mean sizeof?", args[0].position)
        else -> throw CompilerException("weird datatype")
    }
 }
@@ -281,9 +330,9 @@ private fun builtinLen(args: List<Expression>, position: Position, program: Prog

 private fun builtinMkword(args: List<Expression>, position: Position, program: Program): NumericLiteralValue {
    if (args.size != 2)
-        throw SyntaxError("mkword requires lsb and msb arguments", position)
-    val constLsb = args[0].constValue(program) ?: throw NotConstArgumentException()
-    val constMsb = args[1].constValue(program) ?: throw NotConstArgumentException()
+        throw SyntaxError("mkword requires msb and lsb arguments", position)
+    val constMsb = args[0].constValue(program) ?: throw NotConstArgumentException()
+    val constLsb = args[1].constValue(program) ?: throw NotConstArgumentException()
    val result = (constMsb.number.toInt() shl 8) or constLsb.number.toInt()
    return NumericLiteralValue(DataType.UWORD, result, position)
 }
@@ -293,7 +342,7 @@ private fun builtinSin8(args: List<Expression>, position: Position, program: Pro
        throw SyntaxError("sin8 requires one argument", position)
    val constval = args[0].constValue(program) ?: throw NotConstArgumentException()
    val rad = constval.number.toDouble() /256.0 * 2.0 * PI
-    return NumericLiteralValue(DataType.BYTE, (127.0 * sin(rad)).toShort(), position)
+    return NumericLiteralValue(DataType.BYTE, (127.0 * sin(rad)).toInt().toShort(), position)
 }

 private fun builtinSin8u(args: List<Expression>, position: Position, program: Program): NumericLiteralValue {
@@ -301,7 +350,7 @@ private fun builtinSin8u(args: List<Expression>, position: Position, program: Pr
        throw SyntaxError("sin8u requires one argument", position)
    val constval = args[0].constValue(program) ?: throw NotConstArgumentException()
    val rad = constval.number.toDouble() /256.0 * 2.0 * PI
-    return NumericLiteralValue(DataType.UBYTE, (128.0 + 127.5 * sin(rad)).toShort(), position)
+    return NumericLiteralValue(DataType.UBYTE, (128.0 + 127.5 * sin(rad)).toInt().toShort(), position)
 }

 private fun builtinCos8(args: List<Expression>, position: Position, program: Program): NumericLiteralValue {
@@ -309,7 +358,7 @@ private fun builtinCos8(args: List<Expression>, position: Position, program: Pro
        throw SyntaxError("cos8 requires one argument", position)
    val constval = args[0].constValue(program) ?: throw NotConstArgumentException()
    val rad = constval.number.toDouble() /256.0 * 2.0 * PI
-    return NumericLiteralValue(DataType.BYTE, (127.0 * cos(rad)).toShort(), position)
+    return NumericLiteralValue(DataType.BYTE, (127.0 * cos(rad)).toInt().toShort(), position)
 }

 private fun builtinCos8u(args: List<Expression>, position: Position, program: Program): NumericLiteralValue {
@@ -317,7 +366,7 @@ private fun builtinCos8u(args: List<Expression>, position: Position, program: Pr
        throw SyntaxError("cos8u requires one argument", position)
    val constval = args[0].constValue(program) ?: throw NotConstArgumentException()
    val rad = constval.number.toDouble() /256.0 * 2.0 * PI
-    return NumericLiteralValue(DataType.UBYTE, (128.0 + 127.5 * cos(rad)).toShort(), position)
+    return NumericLiteralValue(DataType.UBYTE, (128.0 + 127.5 * cos(rad)).toInt().toShort(), position)
 }

 private fun builtinSin16(args: List<Expression>, position: Position, program: Program): NumericLiteralValue {
@@ -356,7 +405,7 @@ private fun builtinSgn(args: List<Expression>, position: Position, program: Prog
    if (args.size != 1)
        throw SyntaxError("sgn requires one argument", position)
    val constval = args[0].constValue(program) ?: throw NotConstArgumentException()
-    return NumericLiteralValue(DataType.BYTE, constval.number.toDouble().sign.toShort(), position)
+    return NumericLiteralValue(DataType.BYTE, constval.number.toDouble().sign.toInt().toShort(), position)
 }

 private fun numericLiteral(value: Number, position: Position): NumericLiteralValue {
@@ -368,8 +417,8 @@ private fun numericLiteral(value: Number, position: Position): NumericLiteralVal
                floatNum

    return when(tweakedValue) {
-        is Int -> NumericLiteralValue.optimalNumeric(value.toInt(), position)
-        is Short -> NumericLiteralValue.optimalNumeric(value.toInt(), position)
+        is Int -> NumericLiteralValue.optimalInteger(value.toInt(), position)
+        is Short -> NumericLiteralValue.optimalInteger(value.toInt(), position)
        is Byte -> NumericLiteralValue(DataType.UBYTE, value.toShort(), position)
        is Double -> NumericLiteralValue(DataType.FLOAT, value.toDouble(), position)
        is Float -> NumericLiteralValue(DataType.FLOAT, value.toDouble(), position)
@@ -6,8 +6,6 @@ import prog8.ast.Node
 import prog8.ast.Program
 import prog8.ast.base.DataType
 import prog8.ast.base.ParentSentinel
-import prog8.ast.base.VarDeclType
-import prog8.ast.base.initvarsSubName
 import prog8.ast.expressions.FunctionCall
 import prog8.ast.expressions.IdentifierReference
 import prog8.ast.processing.IAstVisitor
@@ -16,8 +14,7 @@ import prog8.compiler.loadAsmIncludeFile

 private val alwaysKeepSubroutines = setOf(
        Pair("main", "start"),
-        Pair("irq", "irq"),
-        Pair("prog8_lib", "init_system")
+        Pair("irq", "irq")
 )

 private val asmJumpRx = Regex("""[\-+a-zA-Z0-9_ \t]+(jmp|jsr)[ \t]+(\S+).*""", RegexOption.IGNORE_CASE)
@@ -26,12 +23,12 @@ private val asmRefRx = Regex("""[\-+a-zA-Z0-9_ \t]+(...)[ \t]+(\S+).*""", RegexO

 class CallGraph(private val program: Program) : IAstVisitor {

-    val modulesImporting = mutableMapOf<Module, List<Module>>().withDefault { mutableListOf() }
-    val modulesImportedBy = mutableMapOf<Module, List<Module>>().withDefault { mutableListOf() }
-    val subroutinesCalling = mutableMapOf<INameScope, List<Subroutine>>().withDefault { mutableListOf() }
-    val subroutinesCalledBy = mutableMapOf<Subroutine, List<Node>>().withDefault { mutableListOf() }
+    val imports = mutableMapOf<Module, List<Module>>().withDefault { mutableListOf() }
+    val importedBy = mutableMapOf<Module, List<Module>>().withDefault { mutableListOf() }
+    val calls = mutableMapOf<INameScope, List<Subroutine>>().withDefault { mutableListOf() }
+    val calledBy = mutableMapOf<Subroutine, List<Node>>().withDefault { mutableListOf() }

-    // TODO  add dataflow graph: what statements use what variables
+    // TODO  add dataflow graph: what statements use what variables - can be used to eliminate unused vars
    val usedSymbols = mutableSetOf<Statement>()

    init {
@@ -57,17 +54,8 @@ class CallGraph(private val program: Program) : IAstVisitor {
            it.importedBy.clear()
            it.imports.clear()

-            it.importedBy.addAll(modulesImportedBy.getValue(it))
-            it.imports.addAll(modulesImporting.getValue(it))
-
-            forAllSubroutines(it) { sub ->
-                sub.calledBy.clear()
-                sub.calls.clear()
-
-                sub.calledBy.addAll(subroutinesCalledBy.getValue(sub))
-                sub.calls.addAll(subroutinesCalling.getValue(sub))
-            }
-
+            it.importedBy.addAll(importedBy.getValue(it))
+            it.imports.addAll(imports.getValue(it))
        }

        val rootmodule = program.modules.first()
@@ -87,8 +75,8 @@ class CallGraph(private val program: Program) : IAstVisitor {
        val thisModule = directive.definingModule()
        if (directive.directive == "%import") {
            val importedModule: Module = program.modules.single { it.name == directive.args[0].name }
-            modulesImporting[thisModule] = modulesImporting.getValue(thisModule).plus(importedModule)
-            modulesImportedBy[importedModule] = modulesImportedBy.getValue(importedModule).plus(thisModule)
+            imports[thisModule] = imports.getValue(thisModule).plus(importedModule)
+            importedBy[importedModule] = importedBy.getValue(importedModule).plus(thisModule)
        } else if (directive.directive == "%asminclude") {
            val asm = loadAsmIncludeFile(directive.args[0].str!!, thisModule.source)
            val scope = directive.definingScope()
@@ -120,7 +108,7 @@ class CallGraph(private val program: Program) : IAstVisitor {

    override fun visit(subroutine: Subroutine) {
        if (Pair(subroutine.definingScope().name, subroutine.name) in alwaysKeepSubroutines
-                || subroutine.name == initvarsSubName || subroutine.definingModule().isLibraryModule) {
+                || subroutine.definingModule().isLibraryModule) {
            // make sure the entrypoint is mentioned in the used symbols
            addNodeAndParentScopes(subroutine)
        }
@@ -128,8 +116,8 @@ class CallGraph(private val program: Program) : IAstVisitor {
    }

    override fun visit(decl: VarDecl) {
-        if (decl.autogeneratedDontRemove || (decl.definingModule().isLibraryModule && decl.type != VarDeclType.VAR)) {
-            // make sure autogenerated vardecls are in the used symbols
+        if (decl.autogeneratedDontRemove || decl.definingModule().isLibraryModule) {
+            // make sure autogenerated vardecls are in the used symbols and are never removed as 'unused'
            addNodeAndParentScopes(decl)
        }

@@ -143,8 +131,8 @@ class CallGraph(private val program: Program) : IAstVisitor {
        val otherSub = functionCall.target.targetSubroutine(program.namespace)
        if (otherSub != null) {
            functionCall.definingSubroutine()?.let { thisSub ->
-                subroutinesCalling[thisSub] = subroutinesCalling.getValue(thisSub).plus(otherSub)
-                subroutinesCalledBy[otherSub] = subroutinesCalledBy.getValue(otherSub).plus(functionCall)
+                calls[thisSub] = calls.getValue(thisSub).plus(otherSub)
+                calledBy[otherSub] = calledBy.getValue(otherSub).plus(functionCall)
            }
        }
        super.visit(functionCall)
@@ -154,8 +142,8 @@ class CallGraph(private val program: Program) : IAstVisitor {
        val otherSub = functionCallStatement.target.targetSubroutine(program.namespace)
        if (otherSub != null) {
            functionCallStatement.definingSubroutine()?.let { thisSub ->
-                subroutinesCalling[thisSub] = subroutinesCalling.getValue(thisSub).plus(otherSub)
-                subroutinesCalledBy[otherSub] = subroutinesCalledBy.getValue(otherSub).plus(functionCallStatement)
+                calls[thisSub] = calls.getValue(thisSub).plus(otherSub)
+                calledBy[otherSub] = calledBy.getValue(otherSub).plus(functionCallStatement)
            }
        }
        super.visit(functionCallStatement)
@@ -165,8 +153,8 @@ class CallGraph(private val program: Program) : IAstVisitor {
        val otherSub = jump.identifier?.targetSubroutine(program.namespace)
        if (otherSub != null) {
            jump.definingSubroutine()?.let { thisSub ->
-                subroutinesCalling[thisSub] = subroutinesCalling.getValue(thisSub).plus(otherSub)
-                subroutinesCalledBy[otherSub] = subroutinesCalledBy.getValue(otherSub).plus(jump)
+                calls[thisSub] = calls.getValue(thisSub).plus(otherSub)
+                calledBy[otherSub] = calledBy.getValue(otherSub).plus(jump)
            }
        }
        super.visit(jump)
@@ -192,14 +180,14 @@ class CallGraph(private val program: Program) : IAstVisitor {
                if (jumptarget != null && (jumptarget[0].isLetter() || jumptarget[0] == '_')) {
                    val node = program.namespace.lookup(jumptarget.split('.'), context)
                    if (node is Subroutine) {
-                        subroutinesCalling[scope] = subroutinesCalling.getValue(scope).plus(node)
-                        subroutinesCalledBy[node] = subroutinesCalledBy.getValue(node).plus(context)
+                        calls[scope] = calls.getValue(scope).plus(node)
+                        calledBy[node] = calledBy.getValue(node).plus(context)
                    } else if (jumptarget.contains('.')) {
                        // maybe only the first part already refers to a subroutine
                        val node2 = program.namespace.lookup(listOf(jumptarget.substringBefore('.')), context)
                        if (node2 is Subroutine) {
-                            subroutinesCalling[scope] = subroutinesCalling.getValue(scope).plus(node2)
-                            subroutinesCalledBy[node2] = subroutinesCalledBy.getValue(node2).plus(context)
+                            calls[scope] = calls.getValue(scope).plus(node2)
+                            calledBy[node2] = calledBy.getValue(node2).plus(context)
                        }
                    }
                }
@@ -211,8 +199,8 @@ class CallGraph(private val program: Program) : IAstVisitor {
                        if (target.contains('.')) {
                            val node = program.namespace.lookup(listOf(target.substringBefore('.')), context)
                            if (node is Subroutine) {
-                                subroutinesCalling[scope] = subroutinesCalling.getValue(scope).plus(node)
-                                subroutinesCalledBy[node] = subroutinesCalledBy.getValue(node).plus(context)
+                                calls[scope] = calls.getValue(scope).plus(node)
+                                calledBy[node] = calledBy.getValue(node).plus(context)
                            }
                        }
                    }
@@ -132,11 +132,11 @@ class ConstExprEvaluator {
    private fun bitwiseand(left: NumericLiteralValue, right: NumericLiteralValue): NumericLiteralValue {
        if(left.type== DataType.UBYTE) {
            if(right.type in IntegerDatatypes) {
-                return NumericLiteralValue(DataType.UBYTE, (left.number.toInt() or (right.number.toInt() and 255)).toShort(), left.position)
+                return NumericLiteralValue(DataType.UBYTE, (left.number.toInt() and (right.number.toInt() and 255)).toShort(), left.position)
            }
        } else if(left.type== DataType.UWORD) {
            if(right.type in IntegerDatatypes) {
-                return NumericLiteralValue(DataType.UWORD, left.number.toInt() or right.number.toInt(), left.position)
+                return NumericLiteralValue(DataType.UWORD, left.number.toInt() and right.number.toInt(), left.position)
            }
        }
        throw ExpressionError("cannot calculate $left & $right", left.position)
@@ -163,7 +163,7 @@ class ConstExprEvaluator {
        val error = "cannot add $left and $right"
        return when (left.type) {
            in IntegerDatatypes -> when (right.type) {
-                in IntegerDatatypes -> NumericLiteralValue.optimalNumeric(left.number.toInt() + right.number.toInt(), left.position)
+                in IntegerDatatypes -> NumericLiteralValue.optimalInteger(left.number.toInt() + right.number.toInt(), left.position)
                DataType.FLOAT -> NumericLiteralValue(DataType.FLOAT, left.number.toInt() + right.number.toDouble(), left.position)
                else -> throw ExpressionError(error, left.position)
            }
@@ -180,7 +180,7 @@ class ConstExprEvaluator {
        val error = "cannot subtract $left and $right"
        return when (left.type) {
            in IntegerDatatypes -> when (right.type) {
-                in IntegerDatatypes -> NumericLiteralValue.optimalNumeric(left.number.toInt() - right.number.toInt(), left.position)
+                in IntegerDatatypes -> NumericLiteralValue.optimalInteger(left.number.toInt() - right.number.toInt(), left.position)
                DataType.FLOAT -> NumericLiteralValue(DataType.FLOAT, left.number.toInt() - right.number.toDouble(), left.position)
                else -> throw ExpressionError(error, left.position)
            }
@@ -197,7 +197,7 @@ class ConstExprEvaluator {
        val error = "cannot multiply ${left.type} and ${right.type}"
        return when (left.type) {
            in IntegerDatatypes -> when (right.type) {
-                in IntegerDatatypes -> NumericLiteralValue.optimalNumeric(left.number.toInt() * right.number.toInt(), left.position)
+                in IntegerDatatypes -> NumericLiteralValue.optimalInteger(left.number.toInt() * right.number.toInt(), left.position)
                DataType.FLOAT -> NumericLiteralValue(DataType.FLOAT, left.number.toInt() * right.number.toDouble(), left.position)
                else -> throw ExpressionError(error, left.position)
            }
@@ -220,7 +220,7 @@ class ConstExprEvaluator {
                in IntegerDatatypes -> {
                    if(right.number.toInt()==0) divideByZeroError(right.position)
                    val result: Int = left.number.toInt() / right.number.toInt()
-                    NumericLiteralValue.optimalNumeric(result, left.position)
+                    NumericLiteralValue.optimalInteger(result, left.position)
                }
                DataType.FLOAT -> {
                    if(right.number.toDouble()==0.0) divideByZeroError(right.position)
@@ -1,704 +0,0 @@
-package prog8.optimizer
-
-import prog8.ast.IFunctionCall
-import prog8.ast.Program
-import prog8.ast.base.*
-import prog8.ast.expressions.*
-import prog8.ast.processing.IAstModifyingVisitor
-import prog8.ast.statements.*
-import prog8.compiler.target.CompilationTarget
-import prog8.functions.BuiltinFunctions
-import kotlin.math.floor
-
-
-class ConstantFolding(private val program: Program, private val errors: ErrorReporter) : IAstModifyingVisitor {
-    var optimizationsDone: Int = 0
-
-    override fun visit(decl: VarDecl): Statement {
-        // the initializer value can't refer to the variable itself (recursive definition)
-        // TODO: use call tree for this?
-        if(decl.value?.referencesIdentifiers(decl.name) == true || decl.arraysize?.index?.referencesIdentifiers(decl.name) == true) {
-            errors.err("recursive var declaration", decl.position)
-            return decl
-        }
-
-        if(decl.type==VarDeclType.CONST || decl.type==VarDeclType.VAR) {
-            if(decl.isArray){
-                if(decl.arraysize==null) {
-                    // for arrays that have no size specifier (or a non-constant one) attempt to deduce the size
-                    val arrayval = decl.value as? ArrayLiteralValue
-                    if(arrayval!=null) {
-                        decl.arraysize = ArrayIndex(NumericLiteralValue.optimalInteger(arrayval.value.size, decl.position), decl.position)
-                        optimizationsDone++
-                    }
-                }
-                else if(decl.arraysize?.size()==null) {
-                    val size = decl.arraysize!!.index.accept(this)
-                    if(size is NumericLiteralValue) {
-                        decl.arraysize = ArrayIndex(size, decl.position)
-                        optimizationsDone++
-                    }
-                }
-            }
-
-            when(decl.datatype) {
-                DataType.FLOAT -> {
-                    // vardecl: for scalar float vars, promote constant integer initialization values to floats
-                    val litval = decl.value as? NumericLiteralValue
-                    if (litval!=null && litval.type in IntegerDatatypes) {
-                        val newValue = NumericLiteralValue(DataType.FLOAT, litval.number.toDouble(), litval.position)
-                        decl.value = newValue
-                        optimizationsDone++
-                        return super.visit(decl)
-                    }
-                }
-                DataType.ARRAY_UB, DataType.ARRAY_B, DataType.ARRAY_UW, DataType.ARRAY_W -> {
-                    val numericLv = decl.value as? NumericLiteralValue
-                    val rangeExpr = decl.value as? RangeExpr
-                    if(rangeExpr!=null) {
-                        // convert the initializer range expression to an actual array
-                        val declArraySize = decl.arraysize?.size()
-                        if(declArraySize!=null && declArraySize!=rangeExpr.size())
-                            errors.err("range expression size doesn't match declared array size", decl.value?.position!!)
-                        val constRange = rangeExpr.toConstantIntegerRange()
-                        if(constRange!=null) {
-                            val eltType = rangeExpr.inferType(program).typeOrElse(DataType.UBYTE)
-                            if(eltType in ByteDatatypes) {
-                                decl.value = ArrayLiteralValue(InferredTypes.InferredType.known(decl.datatype),
-                                        constRange.map { NumericLiteralValue(eltType, it.toShort(), decl.value!!.position) }.toTypedArray(),
-                                        position = decl.value!!.position)
-                            } else {
-                                decl.value = ArrayLiteralValue(InferredTypes.InferredType.known(decl.datatype),
-                                        constRange.map { NumericLiteralValue(eltType, it, decl.value!!.position) }.toTypedArray(),
-                                        position = decl.value!!.position)
-                            }
-                            decl.value!!.linkParents(decl)
-                            optimizationsDone++
-                            return super.visit(decl)
-                        }
-                    }
-                    if(numericLv!=null && numericLv.type== DataType.FLOAT)
-                        errors.err("arraysize requires only integers here", numericLv.position)
-                    val size = decl.arraysize?.size() ?: return decl
-                    if (rangeExpr==null && numericLv!=null) {
-                        // arraysize initializer is empty or a single int, and we know the size; create the arraysize.
-                        val fillvalue = numericLv.number.toInt()
-                        when(decl.datatype){
-                            DataType.ARRAY_UB -> {
-                                if(fillvalue !in 0..255)
-                                    errors.err("ubyte value overflow", numericLv.position)
-                            }
-                            DataType.ARRAY_B -> {
-                                if(fillvalue !in -128..127)
-                                    errors.err("byte value overflow", numericLv.position)
-                            }
-                            DataType.ARRAY_UW -> {
-                                if(fillvalue !in 0..65535)
-                                    errors.err("uword value overflow", numericLv.position)
-                            }
-                            DataType.ARRAY_W -> {
-                                if(fillvalue !in -32768..32767)
-                                    errors.err("word value overflow", numericLv.position)
-                            }
-                            else -> {}
-                        }
-                        // create the array itself, filled with the fillvalue.
-                        val array = Array(size) {fillvalue}.map { NumericLiteralValue.optimalInteger(it, numericLv.position) as Expression}.toTypedArray()
-                        val refValue = ArrayLiteralValue(InferredTypes.InferredType.known(decl.datatype), array, position = numericLv.position)
-                        decl.value = refValue
-                        refValue.parent=decl
-                        optimizationsDone++
-                        return super.visit(decl)
-                    }
-                }
-                DataType.ARRAY_F  -> {
-                    val size = decl.arraysize?.size() ?: return decl
-                    val litval = decl.value as? NumericLiteralValue
-                    if(litval==null) {
-                        // there's no initialization value, but the size is known, so we're ok.
-                        return super.visit(decl)
-                    } else {
-                        // arraysize initializer is a single int, and we know the size.
-                        val fillvalue = litval.number.toDouble()
-                        if (fillvalue < CompilationTarget.machine.FLOAT_MAX_NEGATIVE || fillvalue > CompilationTarget.machine.FLOAT_MAX_POSITIVE)
-                            errors.err("float value overflow", litval.position)
-                        else {
-                            // create the array itself, filled with the fillvalue.
-                            val array = Array(size) {fillvalue}.map { NumericLiteralValue(DataType.FLOAT, it, litval.position) as Expression}.toTypedArray()
-                            val refValue = ArrayLiteralValue(InferredTypes.InferredType.known(DataType.ARRAY_F), array, position = litval.position)
-                            decl.value = refValue
-                            refValue.parent=decl
-                            optimizationsDone++
-                            return super.visit(decl)
-                        }
-                    }
-                }
-                else -> {
-                    // nothing to do for this type
-                    // this includes strings and structs
-                }
-            }
-        }
-
-        return super.visit(decl)
-    }
-
-    /**
-     * replace identifiers that refer to const value, with the value itself (if it's a simple type)
-     */
-    override fun visit(identifier: IdentifierReference): Expression {
-        // don't replace when it's an assignment target or loop variable
-        if(identifier.parent is AssignTarget)
-            return identifier
-        var forloop = identifier.parent as? ForLoop
-        if(forloop==null)
-            forloop = identifier.parent.parent as? ForLoop
-        if(forloop!=null && identifier===forloop.loopVar)
-            return identifier
-
-        return try {
-            val cval = identifier.constValue(program) ?: return identifier
-            return when (cval.type) {
-                in NumericDatatypes -> {
-                    val copy = NumericLiteralValue(cval.type, cval.number, identifier.position)
-                    copy.parent = identifier.parent
-                    copy
-                }
-                in PassByReferenceDatatypes -> throw FatalAstException("pass-by-reference type should not be considered a constant")
-                else -> identifier
-            }
-        } catch (ax: AstException) {
-            errors.err("unhandled AST error: $ax", identifier.position)
-            identifier
-        }
-    }
-
-    override fun visit(functionCall: FunctionCall): Expression {
-        super.visit(functionCall)
-        typeCastConstArguments(functionCall)
-        return try {
-            functionCall.constValue(program) ?: functionCall
-        } catch (ax: AstException) {
-            errors.err("unhandled AST error: $ax", functionCall.position)
-            functionCall
-        }
-    }
-
-    override fun visit(functionCallStatement: FunctionCallStatement): Statement {
-        super.visit(functionCallStatement)
-        typeCastConstArguments(functionCallStatement)
-        return functionCallStatement
-    }
-
-    private fun typeCastConstArguments(functionCall: IFunctionCall) {
-        if(functionCall.target.nameInSource.size==1) {
-            val builtinFunction = BuiltinFunctions[functionCall.target.nameInSource.single()]
-            if(builtinFunction!=null) {
-                // match the arguments of a builtin function signature.
-                for(arg in functionCall.args.withIndex().zip(builtinFunction.parameters)) {
-                    val possibleDts = arg.second.possibleDatatypes
-                    val argConst = arg.first.value.constValue(program)
-                    if(argConst!=null && argConst.type !in possibleDts) {
-                        val convertedValue = argConst.cast(possibleDts.first())
-                        functionCall.args[arg.first.index] = convertedValue
-                        optimizationsDone++
-                    }
-                }
-                return
-            }
-        }
-        // match the arguments of a subroutine.
-        val subroutine = functionCall.target.targetSubroutine(program.namespace)
-        if(subroutine!=null) {
-            // if types differ, try to typecast constant arguments to the function call to the desired data type of the parameter
-            for(arg in functionCall.args.withIndex().zip(subroutine.parameters)) {
-                val expectedDt = arg.second.type
-                val argConst = arg.first.value.constValue(program)
-                if(argConst!=null && argConst.type!=expectedDt) {
-                    val convertedValue = argConst.cast(expectedDt)
-                    functionCall.args[arg.first.index] = convertedValue
-                    optimizationsDone++
-                }
-            }
-        }
-    }
-
-    override fun visit(memread: DirectMemoryRead): Expression {
-        // @( &thing )  -->  thing
-        val addrOf = memread.addressExpression as? AddressOf
-        if(addrOf!=null)
-            return super.visit(addrOf.identifier)
-        return super.visit(memread)
-    }
-
-    /**
-     * Try to accept a unary prefix expression.
-     * Compile-time constant sub expressions will be evaluated on the spot.
-     * For instance, the expression for "- 4.5" will be optimized into the float literal -4.5
-     */
-    override fun visit(expr: PrefixExpression): Expression {
-        return try {
-            val prefixExpr=super.visit(expr)
-            if(prefixExpr !is PrefixExpression)
-                return prefixExpr
-
-            val subexpr = prefixExpr.expression
-            if (subexpr is NumericLiteralValue) {
-                // accept prefixed literal values (such as -3, not true)
-                return when (prefixExpr.operator) {
-                    "+" -> subexpr
-                    "-" -> when (subexpr.type) {
-                        in IntegerDatatypes -> {
-                            optimizationsDone++
-                            NumericLiteralValue.optimalNumeric(-subexpr.number.toInt(), subexpr.position)
-                        }
-                        DataType.FLOAT -> {
-                            optimizationsDone++
-                            NumericLiteralValue(DataType.FLOAT, -subexpr.number.toDouble(), subexpr.position)
-                        }
-                        else -> throw ExpressionError("can only take negative of int or float", subexpr.position)
-                    }
-                    "~" -> when (subexpr.type) {
-                        in IntegerDatatypes -> {
-                            optimizationsDone++
-                            NumericLiteralValue.optimalNumeric(subexpr.number.toInt().inv(), subexpr.position)
-                        }
-                        else -> throw ExpressionError("can only take bitwise inversion of int", subexpr.position)
-                    }
-                    "not" -> {
-                        optimizationsDone++
-                        NumericLiteralValue.fromBoolean(subexpr.number.toDouble() == 0.0, subexpr.position)
-                    }
-                    else -> throw ExpressionError(prefixExpr.operator, subexpr.position)
-                }
-            }
-            return prefixExpr
-        } catch (ax: AstException) {
-            errors.err("unhandled AST error: $ax", expr.position)
-            expr
-        }
-    }
-
-    /**
-     * Try to accept a binary expression.
-     * Compile-time constant sub expressions will be evaluated on the spot.
-     * For instance, "9 * (4 + 2)" will be optimized into the integer literal 54.
-     *
-     * More complex stuff: reordering to group constants:
-     * If one of our operands is a Constant,
-     *   and the other operand is a Binary expression,
-     *   and one of ITS operands is a Constant,
-     *   and ITS other operand is NOT a Constant,
-     *   ...it may be possible to rewrite the expression to group the two Constants together,
-     *      to allow them to be const-folded away.
-     *
-     *  examples include:
-     *        (X / c1) * c2  ->  X / (c2/c1)
-     *        (X + c1) - c2  ->  X + (c1-c2)
-     */
-    override fun visit(expr: BinaryExpression): Expression {
-        return try {
-            super.visit(expr)
-
-            if(expr.left is StringLiteralValue || expr.left is ArrayLiteralValue
-                    || expr.right is StringLiteralValue || expr.right is ArrayLiteralValue)
-                throw FatalAstException("binexpr with reference litval instead of numeric")
-
-            val leftconst = expr.left.constValue(program)
-            val rightconst = expr.right.constValue(program)
-
-            val subExpr: BinaryExpression? = when {
-                leftconst!=null -> expr.right as? BinaryExpression
-                rightconst!=null -> expr.left as? BinaryExpression
-                else -> null
-            }
-            if(subExpr!=null) {
-                val subleftconst = subExpr.left.constValue(program)
-                val subrightconst = subExpr.right.constValue(program)
-                if ((subleftconst != null && subrightconst == null) || (subleftconst==null && subrightconst!=null)) {
-                    // try reordering.
-                    return groupTwoConstsTogether(expr, subExpr,
-                            leftconst != null, rightconst != null,
-                            subleftconst != null, subrightconst != null)
-                }
-            }
-
-            // const fold when both operands are a const
-            return when {
-                leftconst != null && rightconst != null -> {
-                    optimizationsDone++
-                    val evaluator = ConstExprEvaluator()
-                    evaluator.evaluate(leftconst, expr.operator, rightconst)
-                }
-
-                else -> expr
-            }
-        } catch (ax: AstException) {
-            errors.err("unhandled AST error: $ax", expr.position)
-            expr
-        }
-    }
-
-    private fun groupTwoConstsTogether(expr: BinaryExpression,
-                                       subExpr: BinaryExpression,
-                                       leftIsConst: Boolean,
-                                       rightIsConst: Boolean,
-                                       subleftIsConst: Boolean,
-                                       subrightIsConst: Boolean): Expression
-    {
-        // todo: this implements only a small set of possible reorderings at this time
-        if(expr.operator==subExpr.operator) {
-            // both operators are the isSameAs.
-            // If + or *,  we can simply swap the const of expr and Var in subexpr.
-            if(expr.operator=="+" || expr.operator=="*") {
-                if(leftIsConst) {
-                    if(subleftIsConst)
-                        expr.left = subExpr.right.also { subExpr.right = expr.left }
-                    else
-                        expr.left = subExpr.left.also { subExpr.left = expr.left }
-                } else {
-                    if(subleftIsConst)
-                        expr.right = subExpr.right.also {subExpr.right = expr.right }
-                    else
-                        expr.right = subExpr.left.also { subExpr.left = expr.right }
-                }
-                optimizationsDone++
-                return expr
-            }
-
-            // If - or /,  we simetimes must reorder more, and flip operators (- -> +, / -> *)
-            if(expr.operator=="-" || expr.operator=="/") {
-                optimizationsDone++
-                if(leftIsConst) {
-                    return if(subleftIsConst) {
-                        val tmp = subExpr.right
-                        subExpr.right = subExpr.left
-                        subExpr.left = expr.left
-                        expr.left = tmp
-                        expr.operator = if(expr.operator=="-") "+" else "*"
-                        expr
-                    } else
-                        BinaryExpression(
-                                BinaryExpression(expr.left, if (expr.operator == "-") "+" else "*", subExpr.right, subExpr.position),
-                                expr.operator, subExpr.left, expr.position)
-                } else {
-                    return if(subleftIsConst) {
-                        expr.right = subExpr.right.also { subExpr.right = expr.right }
-                        expr
-                    } else
-                        BinaryExpression(
-                                subExpr.left, expr.operator,
-                                BinaryExpression(expr.right, if (expr.operator == "-") "+" else "*", subExpr.right, subExpr.position),
-                                expr.position)
-                }
-            }
-            return expr
-
-        }
-        else
-        {
-
-            if(expr.operator=="/" && subExpr.operator=="*") {
-                optimizationsDone++
-                if(leftIsConst) {
-                    return if(subleftIsConst) {
-                        // C1/(C2*V) -> (C1/C2)/V
-                        BinaryExpression(
-                                BinaryExpression(expr.left, "/", subExpr.left, subExpr.position),
-                                "/",
-                                subExpr.right, expr.position)
-                    } else {
-                        // C1/(V*C2) -> (C1/C2)/V
-                        BinaryExpression(
-                                BinaryExpression(expr.left, "/", subExpr.right, subExpr.position),
-                                "/",
-                                subExpr.left, expr.position)
-                    }
-                } else {
-                    return if(subleftIsConst) {
-                        // (C1*V)/C2 -> (C1/C2)*V
-                        BinaryExpression(
-                                BinaryExpression(subExpr.left, "/", expr.right, subExpr.position),
-                                "*",
-                                subExpr.right, expr.position)
-                    } else {
-                        // (V*C1)/C2 -> (C1/C2)*V
-                        BinaryExpression(
-                                BinaryExpression(subExpr.right, "/", expr.right, subExpr.position),
-                                "*",
-                                subExpr.left, expr.position)
-                    }
-                }
-            }
-            else if(expr.operator=="*" && subExpr.operator=="/") {
-                optimizationsDone++
-                if(leftIsConst) {
-                    return if(subleftIsConst) {
-                        // C1*(C2/V) -> (C1*C2)/V
-                        BinaryExpression(
-                                BinaryExpression(expr.left, "*", subExpr.left, subExpr.position),
-                                "/",
-                                subExpr.right, expr.position)
-                    } else {
-                        // C1*(V/C2) -> (C1/C2)*V
-                        BinaryExpression(
-                                BinaryExpression(expr.left, "/", subExpr.right, subExpr.position),
-                                "*",
-                                subExpr.left, expr.position)
-                    }
-                } else {
-                    return if(subleftIsConst) {
-                        // (C1/V)*C2 -> (C1*C2)/V
-                        BinaryExpression(
-                                BinaryExpression(subExpr.left, "*", expr.right, subExpr.position),
-                                "/",
-                                subExpr.right, expr.position)
-                    } else {
-                        // (V/C1)*C2 -> (C1/C2)*V
-                        BinaryExpression(
-                                BinaryExpression(expr.right, "/", subExpr.right, subExpr.position),
-                                "*",
-                                subExpr.left, expr.position)
-                    }
-                }
-            }
-            else if(expr.operator=="+" && subExpr.operator=="-") {
-                optimizationsDone++
-                if(leftIsConst){
-                    return if(subleftIsConst){
-                        // c1+(c2-v)  ->  (c1+c2)-v
-                        BinaryExpression(
-                                BinaryExpression(expr.left, "+", subExpr.left, subExpr.position),
-                                "-",
-                                subExpr.right, expr.position)
-                    } else {
-                        // c1+(v-c2)  ->  v+(c1-c2)
-                        BinaryExpression(
-                                BinaryExpression(expr.left, "-", subExpr.right, subExpr.position),
-                                "+",
-                                subExpr.left, expr.position)
-                    }
-                } else {
-                    return if(subleftIsConst) {
-                        // (c1-v)+c2  ->  (c1+c2)-v
-                        BinaryExpression(
-                                BinaryExpression(subExpr.left, "+", expr.right, subExpr.position),
-                                "-",
-                                subExpr.right, expr.position)
-                    } else {
-                        // (v-c1)+c2  ->  v+(c2-c1)
-                        BinaryExpression(
-                                BinaryExpression(expr.right, "-", subExpr.right, subExpr.position),
-                                "+",
-                                subExpr.left, expr.position)
-                    }
-                }
-            }
-            else if(expr.operator=="-" && subExpr.operator=="+") {
-                optimizationsDone++
-                if(leftIsConst) {
-                    return if(subleftIsConst) {
-                        // c1-(c2+v)  ->  (c1-c2)-v
-                        BinaryExpression(
-                                BinaryExpression(expr.left, "-", subExpr.left, subExpr.position),
-                                "-",
-                                subExpr.right, expr.position)
-                    } else {
-                        // c1-(v+c2)  ->  (c1-c2)-v
-                        BinaryExpression(
-                                BinaryExpression(expr.left, "-", subExpr.right, subExpr.position),
-                                "-",
-                                subExpr.left, expr.position)
-                    }
-                } else {
-                    return if(subleftIsConst) {
-                        // (c1+v)-c2  ->  v+(c1-c2)
-                        BinaryExpression(
-                                BinaryExpression(subExpr.left, "-", expr.right, subExpr.position),
-                                "+",
-                                subExpr.right, expr.position)
-                    } else {
-                        // (v+c1)-c2  ->  v+(c1-c2)
-                        BinaryExpression(
-                                BinaryExpression(subExpr.right, "-", expr.right, subExpr.position),
-                                "+",
-                                subExpr.left, expr.position)
-                    }
-                }
-            }
-
-            return expr
-        }
-    }
-
-    override fun visit(forLoop: ForLoop): Statement {
-
-        fun adjustRangeDt(rangeFrom: NumericLiteralValue, targetDt: DataType, rangeTo: NumericLiteralValue, stepLiteral: NumericLiteralValue?, range: RangeExpr): RangeExpr {
-            val newFrom: NumericLiteralValue
-            val newTo: NumericLiteralValue
-            try {
-                newFrom = rangeFrom.cast(targetDt)
-                newTo = rangeTo.cast(targetDt)
-            } catch (x: ExpressionError) {
-                return range
-            }
-            val newStep: Expression = try {
-                stepLiteral?.cast(targetDt)?: range.step
-            } catch(ee: ExpressionError) {
-                range.step
-            }
-            return RangeExpr(newFrom, newTo, newStep, range.position)
-        }
-
-        val forLoop2 = super.visit(forLoop) as ForLoop
-
-        // check if we need to adjust an array literal to the loop variable's datatype
-        val array = forLoop2.iterable as? ArrayLiteralValue
-        if(array!=null) {
-            val loopvarDt: DataType = when {
-                forLoop.loopVar!=null -> forLoop.loopVar!!.inferType(program).typeOrElse(DataType.UBYTE)
-                forLoop.loopRegister!=null -> DataType.UBYTE
-                else -> throw FatalAstException("weird for loop")
-            }
-
-            val arrayType = when(loopvarDt) {
-                DataType.UBYTE -> DataType.ARRAY_UB
-                DataType.BYTE -> DataType.ARRAY_B
-                DataType.UWORD -> DataType.ARRAY_UW
-                DataType.WORD -> DataType.ARRAY_W
-                DataType.FLOAT -> DataType.ARRAY_F
-                else -> throw FatalAstException("invalid array elt type")
-            }
-            val array2 = array.cast(arrayType)
-            if(array2!=null && array2!==array) {
-                forLoop2.iterable = array2
-                array2.linkParents(forLoop2)
-            }
-        }
-
-        // adjust the datatype of a range expression in for loops to the loop variable.
-        val iterableRange = forLoop2.iterable as? RangeExpr ?: return forLoop2
-        val rangeFrom = iterableRange.from as? NumericLiteralValue
-        val rangeTo = iterableRange.to as? NumericLiteralValue
-        if(rangeFrom==null || rangeTo==null) return forLoop2
-
-        val loopvar = forLoop2.loopVar?.targetVarDecl(program.namespace)
-        if(loopvar!=null) {
-            val stepLiteral = iterableRange.step as? NumericLiteralValue
-            when(loopvar.datatype) {
-                DataType.UBYTE -> {
-                    if(rangeFrom.type!= DataType.UBYTE) {
-                        // attempt to translate the iterable into ubyte values
-                        forLoop2.iterable = adjustRangeDt(rangeFrom, loopvar.datatype, rangeTo, stepLiteral, iterableRange)
-                    }
-                }
-                DataType.BYTE -> {
-                    if(rangeFrom.type!= DataType.BYTE) {
-                        // attempt to translate the iterable into byte values
-                        forLoop2.iterable = adjustRangeDt(rangeFrom, loopvar.datatype, rangeTo, stepLiteral, iterableRange)
-                    }
-                }
-                DataType.UWORD -> {
-                    if(rangeFrom.type!= DataType.UWORD) {
-                        // attempt to translate the iterable into uword values
-                        forLoop2.iterable = adjustRangeDt(rangeFrom, loopvar.datatype, rangeTo, stepLiteral, iterableRange)
-                    }
-                }
-                DataType.WORD -> {
-                    if(rangeFrom.type!= DataType.WORD) {
-                        // attempt to translate the iterable into word values
-                        forLoop2.iterable = adjustRangeDt(rangeFrom, loopvar.datatype, rangeTo, stepLiteral, iterableRange)
-                    }
-                }
-                else -> throw FatalAstException("invalid loopvar datatype $loopvar")
-            }
-        }
-        return forLoop2
-    }
-
-    override fun visit(arrayLiteral: ArrayLiteralValue): Expression {
-        // because constant folding can result in arrays that are now suddenly capable
-        // of telling the type of all their elements (for instance, when they contained -2 which
-        // was a prefix expression earlier), we recalculate the array's datatype.
-        val array = super.visit(arrayLiteral)
-        if(array is ArrayLiteralValue) {
-            if(array.type.isKnown)
-                return array
-            val arrayDt = array.guessDatatype(program)
-            if(arrayDt.isKnown) {
-                val newArray = arrayLiteral.cast(arrayDt.typeOrElse(DataType.STRUCT))
-                if(newArray!=null)
-                    return newArray
-            }
-        }
-        return array
-    }
-
-    override fun visit(assignment: Assignment): Statement {
-        super.visit(assignment)
-        val lv = assignment.value as? NumericLiteralValue
-        if(lv!=null) {
-            // see if we can promote/convert a literal value to the required datatype
-            val idt = assignment.target.inferType(program, assignment)
-            if(!idt.isKnown)
-                return assignment
-            when(idt.typeOrElse(DataType.STRUCT)) {
-                DataType.UWORD -> {
-                    // we can convert to UWORD: any UBYTE, BYTE/WORD that are >=0, FLOAT that's an integer 0..65535,
-                    if(lv.type== DataType.UBYTE)
-                        assignment.value = NumericLiteralValue(DataType.UWORD, lv.number.toInt(), lv.position)
-                    else if(lv.type== DataType.BYTE && lv.number.toInt()>=0)
-                        assignment.value = NumericLiteralValue(DataType.UWORD, lv.number.toInt(), lv.position)
-                    else if(lv.type== DataType.WORD && lv.number.toInt()>=0)
-                        assignment.value = NumericLiteralValue(DataType.UWORD, lv.number.toInt(), lv.position)
-                    else if(lv.type== DataType.FLOAT) {
-                        val d = lv.number.toDouble()
-                        if(floor(d)==d && d>=0 && d<=65535)
-                            assignment.value = NumericLiteralValue(DataType.UWORD, floor(d).toInt(), lv.position)
-                    }
-                }
-                DataType.UBYTE -> {
-                    // we can convert to UBYTE: UWORD <=255, BYTE >=0, FLOAT that's an integer 0..255,
-                    if(lv.type== DataType.UWORD && lv.number.toInt() <= 255)
-                        assignment.value = NumericLiteralValue(DataType.UBYTE, lv.number.toShort(), lv.position)
-                    else if(lv.type== DataType.BYTE && lv.number.toInt() >=0)
-                        assignment.value = NumericLiteralValue(DataType.UBYTE, lv.number.toShort(), lv.position)
-                    else if(lv.type== DataType.FLOAT) {
-                        val d = lv.number.toDouble()
-                        if(floor(d)==d && d >=0 && d<=255)
-                            assignment.value = NumericLiteralValue(DataType.UBYTE, floor(d).toShort(), lv.position)
-                    }
-                }
-                DataType.BYTE -> {
-                    // we can convert to BYTE: UWORD/UBYTE <= 127, FLOAT that's an integer 0..127
-                    if(lv.type== DataType.UWORD && lv.number.toInt() <= 127)
-                        assignment.value = NumericLiteralValue(DataType.BYTE, lv.number.toShort(), lv.position)
-                    else if(lv.type== DataType.UBYTE && lv.number.toInt() <= 127)
-                        assignment.value = NumericLiteralValue(DataType.BYTE, lv.number.toShort(), lv.position)
-                    else if(lv.type== DataType.FLOAT) {
-                        val d = lv.number.toDouble()
-                        if(floor(d)==d && d>=0 && d<=127)
-                            assignment.value = NumericLiteralValue(DataType.BYTE, floor(d).toShort(), lv.position)
-                    }
-                }
-                DataType.WORD -> {
-                    // we can convert to WORD: any UBYTE/BYTE, UWORD <= 32767, FLOAT that's an integer -32768..32767,
-                    if(lv.type== DataType.UBYTE || lv.type== DataType.BYTE)
-                        assignment.value = NumericLiteralValue(DataType.WORD, lv.number.toInt(), lv.position)
-                    else if(lv.type== DataType.UWORD && lv.number.toInt() <= 32767)
-                        assignment.value = NumericLiteralValue(DataType.WORD, lv.number.toInt(), lv.position)
-                    else if(lv.type== DataType.FLOAT) {
-                        val d = lv.number.toDouble()
-                        if(floor(d)==d && d>=-32768 && d<=32767)
-                            assignment.value = NumericLiteralValue(DataType.BYTE, floor(d).toShort(), lv.position)
-                    }
-                }
-                DataType.FLOAT -> {
-                    assignment.value = NumericLiteralValue(DataType.FLOAT, lv.number.toDouble(), lv.position)
-                }
-                else -> {}
-            }
-        }
-        return assignment
-    }
-}
@@ -0,0 +1,455 @@
+package prog8.optimizer
+
+import prog8.ast.Node
+import prog8.ast.Program
+import prog8.ast.base.*
+import prog8.ast.expressions.*
+import prog8.ast.processing.AstWalker
+import prog8.ast.processing.IAstModification
+import prog8.ast.statements.*
+
+
+internal class ConstantFoldingOptimizer(private val program: Program) : AstWalker() {
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun before(memread: DirectMemoryRead, parent: Node): Iterable<IAstModification> {
+        // @( &thing )  -->  thing
+        val addrOf = memread.addressExpression as? AddressOf
+        return if(addrOf!=null)
+            listOf(IAstModification.ReplaceNode(memread, addrOf.identifier, parent))
+        else
+            noModifications
+    }
+
+    override fun after(expr: PrefixExpression, parent: Node): Iterable<IAstModification> {
+        // Try to turn a unary prefix expression into a single constant value.
+        // Compile-time constant sub expressions will be evaluated on the spot.
+        // For instance, the expression for "- 4.5" will be optimized into the float literal -4.5
+        val subexpr = expr.expression
+        if (subexpr is NumericLiteralValue) {
+            // accept prefixed literal values (such as -3, not true)
+            return when (expr.operator) {
+                "+" -> listOf(IAstModification.ReplaceNode(expr, subexpr, parent))
+                "-" -> when (subexpr.type) {
+                    in IntegerDatatypes -> {
+                        listOf(IAstModification.ReplaceNode(expr,
+                                NumericLiteralValue.optimalInteger(-subexpr.number.toInt(), subexpr.position),
+                                parent))
+                    }
+                    DataType.FLOAT -> {
+                        listOf(IAstModification.ReplaceNode(expr,
+                                NumericLiteralValue(DataType.FLOAT, -subexpr.number.toDouble(), subexpr.position),
+                                parent))
+                    }
+                    else -> throw ExpressionError("can only take negative of int or float", subexpr.position)
+                }
+                "~" -> when (subexpr.type) {
+                    DataType.BYTE -> {
+                        listOf(IAstModification.ReplaceNode(expr,
+                                NumericLiteralValue(DataType.BYTE, subexpr.number.toInt().inv(), subexpr.position),
+                                parent))
+                    }
+                    DataType.UBYTE -> {
+                        listOf(IAstModification.ReplaceNode(expr,
+                                NumericLiteralValue(DataType.UBYTE, subexpr.number.toInt().inv() and 255, subexpr.position),
+                                parent))
+                    }
+                    DataType.WORD -> {
+                        listOf(IAstModification.ReplaceNode(expr,
+                                NumericLiteralValue(DataType.WORD, subexpr.number.toInt().inv(), subexpr.position),
+                                parent))
+                    }
+                    DataType.UWORD -> {
+                        listOf(IAstModification.ReplaceNode(expr,
+                                NumericLiteralValue(DataType.UWORD, subexpr.number.toInt().inv() and 65535, subexpr.position),
+                                parent))
+                    }
+                    else -> throw ExpressionError("can only take bitwise inversion of int", subexpr.position)
+                }
+                "not" -> {
+                    listOf(IAstModification.ReplaceNode(expr,
+                            NumericLiteralValue.fromBoolean(subexpr.number.toDouble() == 0.0, subexpr.position),
+                            parent))
+                }
+                else -> throw ExpressionError(expr.operator, subexpr.position)
+            }
+        }
+        return noModifications
+    }
+
+    /**
+     * Try to constfold a binary expression.
+     * Compile-time constant sub expressions will be evaluated on the spot.
+     * For instance, "9 * (4 + 2)" will be optimized into the integer literal 54.
+     *
+     * More complex stuff: reordering to group constants:
+     * If one of our operands is a Constant,
+     *   and the other operand is a Binary expression,
+     *   and one of ITS operands is a Constant,
+     *   and ITS other operand is NOT a Constant,
+     *   ...it may be possible to rewrite the expression to group the two Constants together,
+     *      to allow them to be const-folded away.
+     *
+     *  examples include:
+     *        (X / c1) * c2  ->  X / (c2/c1)
+     *        (X + c1) - c2  ->  X + (c1-c2)
+     */
+    override fun after(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
+        val leftconst = expr.left.constValue(program)
+        val rightconst = expr.right.constValue(program)
+
+        val subExpr: BinaryExpression? = when {
+            leftconst!=null -> expr.right as? BinaryExpression
+            rightconst!=null -> expr.left as? BinaryExpression
+            else -> null
+        }
+        if(subExpr!=null) {
+            val subleftconst = subExpr.left.constValue(program)
+            val subrightconst = subExpr.right.constValue(program)
+            if ((subleftconst != null && subrightconst == null) || (subleftconst==null && subrightconst!=null)) {
+                // try reordering.
+                val change = groupTwoConstsTogether(expr, subExpr,
+                        leftconst != null, rightconst != null,
+                        subleftconst != null, subrightconst != null)
+                return change?.let { listOf(it) } ?: noModifications
+            }
+        }
+
+        // const fold when both operands are a const
+        if(leftconst != null && rightconst != null) {
+            val evaluator = ConstExprEvaluator()
+            val result = evaluator.evaluate(leftconst, expr.operator, rightconst)
+            return listOf(IAstModification.ReplaceNode(expr, result, parent))
+        }
+
+        return noModifications
+    }
+
+    override fun after(array: ArrayLiteralValue, parent: Node): Iterable<IAstModification> {
+        // because constant folding can result in arrays that are now suddenly capable
+        // of telling the type of all their elements (for instance, when they contained -2 which
+        // was a prefix expression earlier), we recalculate the array's datatype.
+        if(array.type.isKnown)
+            return noModifications
+
+        // if the array literalvalue is inside an array vardecl, take the type from that
+        // otherwise infer it from the elements of the array
+        val vardeclType = (array.parent as? VarDecl)?.datatype
+        if(vardeclType!=null) {
+            val newArray = array.cast(vardeclType)
+            if (newArray != null && newArray != array)
+                return listOf(IAstModification.ReplaceNode(array, newArray, parent))
+        } else {
+            val arrayDt = array.guessDatatype(program)
+            if (arrayDt.isKnown) {
+                val newArray = array.cast(arrayDt.typeOrElse(DataType.STRUCT))
+                if (newArray != null && newArray != array)
+                    return listOf(IAstModification.ReplaceNode(array, newArray, parent))
+            }
+        }
+
+        return noModifications
+    }
+
+    override fun after(functionCall: FunctionCall, parent: Node): Iterable<IAstModification> {
+        // the args of a fuction are constfolded via recursion already.
+        val constvalue = functionCall.constValue(program)
+        return if(constvalue!=null)
+            listOf(IAstModification.ReplaceNode(functionCall, constvalue, parent))
+        else
+            noModifications
+    }
+
+    override fun after(forLoop: ForLoop, parent: Node): Iterable<IAstModification> {
+        fun adjustRangeDt(rangeFrom: NumericLiteralValue, targetDt: DataType, rangeTo: NumericLiteralValue, stepLiteral: NumericLiteralValue?, range: RangeExpr): RangeExpr? {
+            val fromCast = rangeFrom.cast(targetDt)
+            val toCast = rangeTo.cast(targetDt)
+            if(!fromCast.isValid || !toCast.isValid)
+                return null
+
+            val newStep =
+                if(stepLiteral!=null) {
+                    val stepCast = stepLiteral.cast(targetDt)
+                    if(stepCast.isValid)
+                        stepCast.valueOrZero()
+                    else
+                        range.step
+                } else {
+                    range.step
+                }
+
+            return RangeExpr(fromCast.valueOrZero(), toCast.valueOrZero(), newStep, range.position)
+        }
+
+        // adjust the datatype of a range expression in for loops to the loop variable.
+        val iterableRange = forLoop.iterable as? RangeExpr ?: return noModifications
+        val rangeFrom = iterableRange.from as? NumericLiteralValue
+        val rangeTo = iterableRange.to as? NumericLiteralValue
+        if(rangeFrom==null || rangeTo==null) return noModifications
+
+        val loopvar = forLoop.loopVar.targetVarDecl(program.namespace)!!
+        val stepLiteral = iterableRange.step as? NumericLiteralValue
+        when(loopvar.datatype) {
+            DataType.UBYTE -> {
+                if(rangeFrom.type!= DataType.UBYTE) {
+                    // attempt to translate the iterable into ubyte values
+                    val newIter = adjustRangeDt(rangeFrom, loopvar.datatype, rangeTo, stepLiteral, iterableRange)
+                    if(newIter!=null)
+                        return listOf(IAstModification.ReplaceNode(forLoop.iterable, newIter, forLoop))
+                }
+            }
+            DataType.BYTE -> {
+                if(rangeFrom.type!= DataType.BYTE) {
+                    // attempt to translate the iterable into byte values
+                    val newIter = adjustRangeDt(rangeFrom, loopvar.datatype, rangeTo, stepLiteral, iterableRange)
+                    if(newIter!=null)
+                        return listOf(IAstModification.ReplaceNode(forLoop.iterable, newIter, forLoop))
+                }
+            }
+            DataType.UWORD -> {
+                if(rangeFrom.type!= DataType.UWORD) {
+                    // attempt to translate the iterable into uword values
+                    val newIter = adjustRangeDt(rangeFrom, loopvar.datatype, rangeTo, stepLiteral, iterableRange)
+                    if(newIter!=null)
+                        return listOf(IAstModification.ReplaceNode(forLoop.iterable, newIter, forLoop))
+                }
+            }
+            DataType.WORD -> {
+                if(rangeFrom.type!= DataType.WORD) {
+                    // attempt to translate the iterable into word values
+                    val newIter = adjustRangeDt(rangeFrom, loopvar.datatype, rangeTo, stepLiteral, iterableRange)
+                    if(newIter!=null)
+                        return listOf(IAstModification.ReplaceNode(forLoop.iterable, newIter, forLoop))
+                }
+            }
+            else -> throw FatalAstException("invalid loopvar datatype $loopvar")
+        }
+
+        return noModifications
+    }
+
+    override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
+        val numval = decl.value as? NumericLiteralValue
+        if(decl.type== VarDeclType.CONST && numval!=null) {
+            val valueDt = numval.inferType(program)
+            if(!valueDt.istype(decl.datatype)) {
+                val cast = numval.cast(decl.datatype)
+                if(cast.isValid)
+                    return listOf(IAstModification.ReplaceNode(numval, cast.valueOrZero(), decl))
+            }
+        }
+        return noModifications
+    }
+
+    private class ShuffleOperands(val expr: BinaryExpression,
+                                  val exprOperator: String?,
+                                  val subExpr: BinaryExpression,
+                                  val newExprLeft: Expression?,
+                                  val newExprRight: Expression?,
+                                  val newSubexprLeft: Expression?,
+                                  val newSubexprRight: Expression?
+                                  ): IAstModification {
+        override fun perform() {
+            if(exprOperator!=null) expr.operator = exprOperator
+            if(newExprLeft!=null) expr.left = newExprLeft
+            if(newExprRight!=null) expr.right = newExprRight
+            if(newSubexprLeft!=null) subExpr.left = newSubexprLeft
+            if(newSubexprRight!=null) subExpr.right = newSubexprRight
+        }
+    }
+
+    private fun groupTwoConstsTogether(expr: BinaryExpression,
+                                       subExpr: BinaryExpression,
+                                       leftIsConst: Boolean,
+                                       rightIsConst: Boolean,
+                                       subleftIsConst: Boolean,
+                                       subrightIsConst: Boolean): IAstModification?
+    {
+        // todo: this implements only a small set of possible reorderings at this time
+        if(expr.operator==subExpr.operator) {
+            // both operators are the same.
+
+            // If associative,  we can simply shuffle the const operands around to optimize.
+            if(expr.operator in associativeOperators) {
+                return if(leftIsConst) {
+                    if(subleftIsConst)
+                        ShuffleOperands(expr, null, subExpr, subExpr.right, null, null, expr.left)
+                    else
+                        ShuffleOperands(expr, null, subExpr, subExpr.left, null, expr.left, null)
+                } else {
+                    if(subleftIsConst)
+                        ShuffleOperands(expr, null, subExpr, null, subExpr.right, null, expr.right)
+                    else
+                        ShuffleOperands(expr, null, subExpr, null, subExpr.left, expr.right, null)
+                }
+            }
+
+            // If - or /,  we simetimes must reorder more, and flip operators (- -> +, / -> *)
+            if(expr.operator=="-" || expr.operator=="/") {
+                if(leftIsConst) {
+                    return if (subleftIsConst) {
+                        ShuffleOperands(expr, if (expr.operator == "-") "+" else "*", subExpr, subExpr.right, null, expr.left, subExpr.left)
+                    } else {
+                        IAstModification.ReplaceNode(expr,
+                                BinaryExpression(
+                                        BinaryExpression(expr.left, if (expr.operator == "-") "+" else "*", subExpr.right, subExpr.position),
+                                        expr.operator, subExpr.left, expr.position),
+                                expr.parent)
+                    }
+                } else {
+                    return if(subleftIsConst) {
+                        return ShuffleOperands(expr, null, subExpr, null, subExpr.right, null, expr.right)
+                    } else {
+                        IAstModification.ReplaceNode(expr,
+                                BinaryExpression(
+                                        subExpr.left, expr.operator,
+                                        BinaryExpression(expr.right, if (expr.operator == "-") "+" else "*", subExpr.right, subExpr.position),
+                                        expr.position),
+                                expr.parent)
+                    }
+                }
+            }
+            return null
+
+        }
+        else
+        {
+
+            if(expr.operator=="/" && subExpr.operator=="*") {
+                if(leftIsConst) {
+                    val change = if(subleftIsConst) {
+                        // C1/(C2*V) -> (C1/C2)/V
+                        BinaryExpression(
+                                BinaryExpression(expr.left, "/", subExpr.left, subExpr.position),
+                                "/",
+                                subExpr.right, expr.position)
+                    } else {
+                        // C1/(V*C2) -> (C1/C2)/V
+                        BinaryExpression(
+                                BinaryExpression(expr.left, "/", subExpr.right, subExpr.position),
+                                "/",
+                                subExpr.left, expr.position)
+                    }
+                    return IAstModification.ReplaceNode(expr, change, expr.parent)
+                } else {
+                    val change = if(subleftIsConst) {
+                        // (C1*V)/C2 -> (C1/C2)*V
+                        BinaryExpression(
+                                BinaryExpression(subExpr.left, "/", expr.right, subExpr.position),
+                                "*",
+                                subExpr.right, expr.position)
+                    } else {
+                        // (V*C1)/C2 -> (C1/C2)*V
+                        BinaryExpression(
+                                BinaryExpression(subExpr.right, "/", expr.right, subExpr.position),
+                                "*",
+                                subExpr.left, expr.position)
+                    }
+                    return IAstModification.ReplaceNode(expr, change, expr.parent)
+                }
+            }
+            else if(expr.operator=="*" && subExpr.operator=="/") {
+                if(leftIsConst) {
+                    val change = if(subleftIsConst) {
+                        // C1*(C2/V) -> (C1*C2)/V
+                        BinaryExpression(
+                                BinaryExpression(expr.left, "*", subExpr.left, subExpr.position),
+                                "/",
+                                subExpr.right, expr.position)
+                    } else {
+                        // C1*(V/C2) -> (C1/C2)*V
+                        BinaryExpression(
+                                BinaryExpression(expr.left, "/", subExpr.right, subExpr.position),
+                                "*",
+                                subExpr.left, expr.position)
+                    }
+                    return IAstModification.ReplaceNode(expr, change, expr.parent)
+                } else {
+                    val change = if(subleftIsConst) {
+                        // (C1/V)*C2 -> (C1*C2)/V
+                        BinaryExpression(
+                                BinaryExpression(subExpr.left, "*", expr.right, subExpr.position),
+                                "/",
+                                subExpr.right, expr.position)
+                    } else {
+                        // (V/C1)*C2 -> (C1/C2)*V
+                        BinaryExpression(
+                                BinaryExpression(expr.right, "/", subExpr.right, subExpr.position),
+                                "*",
+                                subExpr.left, expr.position)
+                    }
+                    return IAstModification.ReplaceNode(expr, change, expr.parent)
+                }
+            }
+            else if(expr.operator=="+" && subExpr.operator=="-") {
+                if(leftIsConst){
+                    val change = if(subleftIsConst){
+                        // c1+(c2-v)  ->  (c1+c2)-v
+                        BinaryExpression(
+                                BinaryExpression(expr.left, "+", subExpr.left, subExpr.position),
+                                "-",
+                                subExpr.right, expr.position)
+                    } else {
+                        // c1+(v-c2)  ->  v+(c1-c2)
+                        BinaryExpression(
+                                BinaryExpression(expr.left, "-", subExpr.right, subExpr.position),
+                                "+",
+                                subExpr.left, expr.position)
+                    }
+                    return IAstModification.ReplaceNode(expr, change, expr.parent)
+                } else {
+                    val change = if(subleftIsConst) {
+                        // (c1-v)+c2  ->  (c1+c2)-v
+                        BinaryExpression(
+                                BinaryExpression(subExpr.left, "+", expr.right, subExpr.position),
+                                "-",
+                                subExpr.right, expr.position)
+                    } else {
+                        // (v-c1)+c2  ->  v+(c2-c1)
+                        BinaryExpression(
+                                BinaryExpression(expr.right, "-", subExpr.right, subExpr.position),
+                                "+",
+                                subExpr.left, expr.position)
+                    }
+                    return IAstModification.ReplaceNode(expr, change, expr.parent)
+                }
+            }
+            else if(expr.operator=="-" && subExpr.operator=="+") {
+                if(leftIsConst) {
+                    val change = if(subleftIsConst) {
+                        // c1-(c2+v)  ->  (c1-c2)-v
+                        BinaryExpression(
+                                BinaryExpression(expr.left, "-", subExpr.left, subExpr.position),
+                                "-",
+                                subExpr.right, expr.position)
+                    } else {
+                        // c1-(v+c2)  ->  (c1-c2)-v
+                        BinaryExpression(
+                                BinaryExpression(expr.left, "-", subExpr.right, subExpr.position),
+                                "-",
+                                subExpr.left, expr.position)
+                    }
+                    return IAstModification.ReplaceNode(expr, change, expr.parent)
+                } else {
+                    val change = if(subleftIsConst) {
+                        // (c1+v)-c2  ->  v+(c1-c2)
+                        BinaryExpression(
+                                BinaryExpression(subExpr.left, "-", expr.right, subExpr.position),
+                                "+",
+                                subExpr.right, expr.position)
+                    } else {
+                        // (v+c1)-c2  ->  v+(c1-c2)
+                        BinaryExpression(
+                                BinaryExpression(subExpr.right, "-", expr.right, subExpr.position),
+                                "+",
+                                subExpr.left, expr.position)
+                    }
+                    return IAstModification.ReplaceNode(expr, change, expr.parent)
+                }
+            }
+
+            return null
+        }
+    }
+
+}
@@ -0,0 +1,192 @@
+package prog8.optimizer
+
+import prog8.ast.Node
+import prog8.ast.Program
+import prog8.ast.base.*
+import prog8.ast.expressions.*
+import prog8.ast.processing.AstWalker
+import prog8.ast.processing.IAstModification
+import prog8.ast.statements.ArrayIndex
+import prog8.ast.statements.AssignTarget
+import prog8.ast.statements.ForLoop
+import prog8.ast.statements.VarDecl
+import prog8.compiler.target.CompilationTarget
+
+// Fix up the literal value's type to match that of the vardecl
+internal class VarConstantValueTypeAdjuster(private val program: Program, private val errors: ErrorReporter) : AstWalker() {
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
+        val declConstValue = decl.value?.constValue(program)
+        if(declConstValue!=null && (decl.type==VarDeclType.VAR || decl.type==VarDeclType.CONST)
+                && !declConstValue.inferType(program).istype(decl.datatype)) {
+            // cast the numeric literal to the appropriate datatype of the variable
+            val cast = declConstValue.cast(decl.datatype)
+            if(cast.isValid)
+                return listOf(IAstModification.ReplaceNode(decl.value!!, cast.valueOrZero(), decl))
+        }
+        return noModifications
+    }
+}
+
+
+// Replace all constant identifiers with their actual value,
+// and the array var initializer values and sizes.
+// This is needed because further constant optimizations depend on those.
+internal class ConstantIdentifierReplacer(private val program: Program, private val errors: ErrorReporter) : AstWalker() {
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun after(identifier: IdentifierReference, parent: Node): Iterable<IAstModification> {
+        // replace identifiers that refer to const value, with the value itself
+        // if it's a simple type and if it's not a left hand side variable
+        if(identifier.parent is AssignTarget)
+            return noModifications
+        var forloop = identifier.parent as? ForLoop
+        if(forloop==null)
+            forloop = identifier.parent.parent as? ForLoop
+        if(forloop!=null && identifier===forloop.loopVar)
+            return noModifications
+
+        val cval = identifier.constValue(program) ?: return noModifications
+        return when (cval.type) {
+            in NumericDatatypes -> listOf(IAstModification.ReplaceNode(identifier, NumericLiteralValue(cval.type, cval.number, identifier.position), identifier.parent))
+            in PassByReferenceDatatypes -> throw FatalAstException("pass-by-reference type should not be considered a constant")
+            else -> noModifications
+        }
+    }
+
+    override fun before(decl: VarDecl, parent: Node): Iterable<IAstModification> {
+        // the initializer value can't refer to the variable itself (recursive definition)
+        // TODO: use call graph for this?
+        if(decl.value?.referencesIdentifiers(decl.name) == true || decl.arraysize?.index?.referencesIdentifiers(decl.name) == true) {
+            errors.err("recursive var declaration", decl.position)
+            return noModifications
+        }
+
+        if(decl.type== VarDeclType.CONST || decl.type== VarDeclType.VAR) {
+            if(decl.isArray){
+                if(decl.arraysize==null) {
+                    // for arrays that have no size specifier (or a non-constant one) attempt to deduce the size
+                    val arrayval = decl.value as? ArrayLiteralValue
+                    if(arrayval!=null) {
+                        return listOf(IAstModification.SetExpression(
+                                { decl.arraysize = ArrayIndex(it, decl.position) },
+                                NumericLiteralValue.optimalInteger(arrayval.value.size, decl.position),
+                                decl
+                        ))
+                    }
+                }
+                else if(decl.arraysize?.constIndex()==null) {
+                    val size = decl.arraysize!!.index.constValue(program)
+                    if(size!=null) {
+                        return listOf(IAstModification.SetExpression(
+                                { decl.arraysize = ArrayIndex(it, decl.position) },
+                                size, decl
+                        ))
+                    }
+                }
+            }
+
+            when(decl.datatype) {
+                DataType.FLOAT -> {
+                    // vardecl: for scalar float vars, promote constant integer initialization values to floats
+                    val litval = decl.value as? NumericLiteralValue
+                    if (litval!=null && litval.type in IntegerDatatypes) {
+                        val newValue = NumericLiteralValue(DataType.FLOAT, litval.number.toDouble(), litval.position)
+                        return listOf(IAstModification.ReplaceNode(decl.value!!, newValue, decl))
+                    }
+                }
+                DataType.ARRAY_UB, DataType.ARRAY_B, DataType.ARRAY_UW, DataType.ARRAY_W -> {
+                    val numericLv = decl.value as? NumericLiteralValue
+                    val rangeExpr = decl.value as? RangeExpr
+                    if(rangeExpr!=null) {
+                        // convert the initializer range expression to an actual array
+                        val declArraySize = decl.arraysize?.constIndex()
+                        if(declArraySize!=null && declArraySize!=rangeExpr.size())
+                            errors.err("range expression size doesn't match declared array size", decl.value?.position!!)
+                        val constRange = rangeExpr.toConstantIntegerRange()
+                        if(constRange!=null) {
+                            val eltType = rangeExpr.inferType(program).typeOrElse(DataType.UBYTE)
+                            val newValue = if(eltType in ByteDatatypes) {
+                                ArrayLiteralValue(InferredTypes.InferredType.known(decl.datatype),
+                                        constRange.map { NumericLiteralValue(eltType, it.toShort(), decl.value!!.position) }.toTypedArray(),
+                                        position = decl.value!!.position)
+                            } else {
+                                ArrayLiteralValue(InferredTypes.InferredType.known(decl.datatype),
+                                        constRange.map { NumericLiteralValue(eltType, it, decl.value!!.position) }.toTypedArray(),
+                                        position = decl.value!!.position)
+                            }
+                            return listOf(IAstModification.ReplaceNode(decl.value!!, newValue, decl))
+                        }
+                    }
+                    if(numericLv!=null && numericLv.type== DataType.FLOAT)
+                        errors.err("arraysize requires only integers here", numericLv.position)
+                    val size = decl.arraysize?.constIndex() ?: return noModifications
+                    if (rangeExpr==null && numericLv!=null) {
+                        // arraysize initializer is empty or a single int, and we know the size; create the arraysize.
+                        val fillvalue = numericLv.number.toInt()
+                        when(decl.datatype){
+                            DataType.ARRAY_UB -> {
+                                if(fillvalue !in 0..255)
+                                    errors.err("ubyte value overflow", numericLv.position)
+                            }
+                            DataType.ARRAY_B -> {
+                                if(fillvalue !in -128..127)
+                                    errors.err("byte value overflow", numericLv.position)
+                            }
+                            DataType.ARRAY_UW -> {
+                                if(fillvalue !in 0..65535)
+                                    errors.err("uword value overflow", numericLv.position)
+                            }
+                            DataType.ARRAY_W -> {
+                                if(fillvalue !in -32768..32767)
+                                    errors.err("word value overflow", numericLv.position)
+                            }
+                            else -> {}
+                        }
+                        // create the array itself, filled with the fillvalue.
+                        val array = Array(size) {fillvalue}.map { NumericLiteralValue(ArrayElementTypes.getValue(decl.datatype), it, numericLv.position) }.toTypedArray<Expression>()
+                        val refValue = ArrayLiteralValue(InferredTypes.InferredType.known(decl.datatype), array, position = numericLv.position)
+                        return listOf(IAstModification.ReplaceNode(decl.value!!, refValue, decl))
+                    }
+                }
+                DataType.ARRAY_F -> {
+                    val size = decl.arraysize?.constIndex() ?: return noModifications
+                    val litval = decl.value as? NumericLiteralValue
+                    val rangeExpr = decl.value as? RangeExpr
+                    if(rangeExpr!=null) {
+                        // convert the initializer range expression to an actual array of floats
+                        val declArraySize = decl.arraysize?.constIndex()
+                        if(declArraySize!=null && declArraySize!=rangeExpr.size())
+                            errors.err("range expression size doesn't match declared array size", decl.value?.position!!)
+                        val constRange = rangeExpr.toConstantIntegerRange()
+                        if(constRange!=null) {
+                            val newValue = ArrayLiteralValue(InferredTypes.InferredType.known(DataType.ARRAY_F),
+                                    constRange.map { NumericLiteralValue(DataType.FLOAT, it.toDouble(), decl.value!!.position) }.toTypedArray(),
+                                    position = decl.value!!.position)
+                            return listOf(IAstModification.ReplaceNode(decl.value!!, newValue, decl))
+                        }
+                    }
+                    if(rangeExpr==null && litval!=null) {
+                        // arraysize initializer is a single int, and we know the size.
+                        val fillvalue = litval.number.toDouble()
+                        if (fillvalue < CompilationTarget.instance.machine.FLOAT_MAX_NEGATIVE || fillvalue > CompilationTarget.instance.machine.FLOAT_MAX_POSITIVE)
+                            errors.err("float value overflow", litval.position)
+                        else {
+                            // create the array itself, filled with the fillvalue.
+                            val array = Array(size) {fillvalue}.map { NumericLiteralValue(DataType.FLOAT, it, litval.position) }.toTypedArray<Expression>()
+                            val refValue = ArrayLiteralValue(InferredTypes.InferredType.known(DataType.ARRAY_F), array, position = litval.position)
+                            return listOf(IAstModification.ReplaceNode(decl.value!!, refValue, decl))
+                        }
+                    }
+                }
+                else -> {
+                    // nothing to do for this type
+                    // this includes strings and structs
+                }
+            }
+        }
+
+        return noModifications
+    }
+}
@@ -0,0 +1,707 @@
+package prog8.optimizer
+
+import prog8.ast.Node
+import prog8.ast.Program
+import prog8.ast.base.*
+import prog8.ast.expressions.*
+import prog8.ast.processing.AstWalker
+import prog8.ast.processing.IAstModification
+import kotlin.math.abs
+import kotlin.math.log2
+import kotlin.math.pow
+
+/*
+    todo add more expression optimizations
+
+    Investigate what optimizations binaryen has, also see  https://egorbo.com/peephole-optimizations.html
+
+ */
+
+
+internal class ExpressionSimplifier(private val program: Program) : AstWalker() {
+    private val powersOfTwo = (1..16).map { (2.0).pow(it) }.toSet()
+    private val negativePowersOfTwo = powersOfTwo.map { -it }.toSet()
+    private val noModifications = emptyList<IAstModification>()
+
+    override fun after(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> {
+        val mods = mutableListOf<IAstModification>()
+
+        // try to statically convert a literal value into one of the desired type
+        val literal = typecast.expression as? NumericLiteralValue
+        if (literal != null) {
+            val newLiteral = literal.cast(typecast.type)
+            if (newLiteral.isValid && newLiteral.valueOrZero() !== literal)
+                mods += IAstModification.ReplaceNode(typecast.expression, newLiteral.valueOrZero(), typecast)
+        }
+
+        // remove redundant nested typecasts
+        val subTypecast = typecast.expression as? TypecastExpression
+        if (subTypecast != null) {
+            // remove the sub-typecast if its datatype is larger than the outer typecast
+            if(subTypecast.type largerThan typecast.type) {
+                mods += IAstModification.ReplaceNode(typecast.expression, subTypecast.expression, typecast)
+            }
+        } else {
+            if (typecast.expression.inferType(program).istype(typecast.type)) {
+                // remove duplicate cast
+                mods += IAstModification.ReplaceNode(typecast, typecast.expression, parent)
+            }
+        }
+
+        return mods
+    }
+
+    override fun before(expr: PrefixExpression, parent: Node): Iterable<IAstModification> {
+        if (expr.operator == "+") {
+            // +X --> X
+            return listOf(IAstModification.ReplaceNode(expr, expr.expression, parent))
+        } else if (expr.operator == "not") {
+            when(expr.expression) {
+                is PrefixExpression -> {
+                    // NOT(NOT(...)) -> ...
+                    val pe = expr.expression as PrefixExpression
+                    if(pe.operator == "not")
+                        return listOf(IAstModification.ReplaceNode(expr, pe.expression, parent))
+                }
+                is BinaryExpression -> {
+                    // NOT (xxxx)  ->   invert the xxxx
+                    val be = expr.expression as BinaryExpression
+                    val newExpr = when (be.operator) {
+                        "<" -> BinaryExpression(be.left, ">=", be.right, be.position)
+                        ">" -> BinaryExpression(be.left, "<=", be.right, be.position)
+                        "<=" -> BinaryExpression(be.left, ">", be.right, be.position)
+                        ">=" -> BinaryExpression(be.left, "<", be.right, be.position)
+                        "==" -> BinaryExpression(be.left, "!=", be.right, be.position)
+                        "!=" -> BinaryExpression(be.left, "==", be.right, be.position)
+                        else -> null
+                    }
+
+                    if (newExpr != null)
+                        return listOf(IAstModification.ReplaceNode(expr, newExpr, parent))
+                }
+                else -> return noModifications
+            }
+        }
+        return noModifications
+    }
+
+    override fun after(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
+        val leftVal = expr.left.constValue(program)
+        val rightVal = expr.right.constValue(program)
+
+        val leftIDt = expr.left.inferType(program)
+        val rightIDt = expr.right.inferType(program)
+        if (!leftIDt.isKnown || !rightIDt.isKnown)
+            throw FatalAstException("can't determine datatype of both expression operands $expr")
+
+        // ConstValue <associativeoperator> X -->  X <associativeoperator> ConstValue
+        if (leftVal != null && expr.operator in associativeOperators && rightVal == null)
+            return listOf(IAstModification.SwapOperands(expr))
+
+        // X + (-A)  -->  X - A
+        if (expr.operator == "+" && (expr.right as? PrefixExpression)?.operator == "-") {
+            return listOf(IAstModification.ReplaceNode(
+                    expr,
+                    BinaryExpression(expr.left, "-", (expr.right as PrefixExpression).expression, expr.position),
+                    parent
+            ))
+        }
+
+        // (-A) + X  -->  X - A
+        if (expr.operator == "+" && (expr.left as? PrefixExpression)?.operator == "-") {
+            return listOf(IAstModification.ReplaceNode(
+                    expr,
+                    BinaryExpression(expr.right, "-", (expr.left as PrefixExpression).expression, expr.position),
+                    parent
+            ))
+        }
+
+        // X - (-A)  -->  X + A
+        if (expr.operator == "-" && (expr.right as? PrefixExpression)?.operator == "-") {
+            return listOf(IAstModification.ReplaceNode(
+                    expr,
+                    BinaryExpression(expr.left, "+", (expr.right as PrefixExpression).expression, expr.position),
+                    parent
+            ))
+        }
+
+        val leftDt = leftIDt.typeOrElse(DataType.STRUCT)
+        val rightDt = rightIDt.typeOrElse(DataType.STRUCT)
+
+        if (expr.operator == "+" || expr.operator == "-"
+                && leftVal == null && rightVal == null
+                && leftDt in NumericDatatypes && rightDt in NumericDatatypes) {
+            val leftBinExpr = expr.left as? BinaryExpression
+            val rightBinExpr = expr.right as? BinaryExpression
+            if (leftBinExpr?.operator == "*") {
+                if (expr.operator == "+") {
+                    // Y*X + X  ->  X*(Y + 1)
+                    // X*Y + X  ->  X*(Y + 1)
+                    val x = expr.right
+                    val y = determineY(x, leftBinExpr)
+                    if (y != null) {
+                        val yPlus1 = BinaryExpression(y, "+", NumericLiteralValue(leftDt, 1, y.position), y.position)
+                        val newExpr = BinaryExpression(x, "*", yPlus1, x.position)
+                        return listOf(IAstModification.ReplaceNode(expr, newExpr, parent))
+                    }
+                } else {
+                    // Y*X - X  ->  X*(Y - 1)
+                    // X*Y - X  ->  X*(Y - 1)
+                    val x = expr.right
+                    val y = determineY(x, leftBinExpr)
+                    if (y != null) {
+                        val yMinus1 = BinaryExpression(y, "-", NumericLiteralValue(leftDt, 1, y.position), y.position)
+                        val newExpr = BinaryExpression(x, "*", yMinus1, x.position)
+                        return listOf(IAstModification.ReplaceNode(expr, newExpr, parent))
+                    }
+                }
+            } else if (rightBinExpr?.operator == "*") {
+                if (expr.operator == "+") {
+                    // X + Y*X  ->  X*(Y + 1)
+                    // X + X*Y  ->  X*(Y + 1)
+                    val x = expr.left
+                    val y = determineY(x, rightBinExpr)
+                    if (y != null) {
+                        val yPlus1 = BinaryExpression(y, "+", NumericLiteralValue.optimalInteger(1, y.position), y.position)
+                        val newExpr = BinaryExpression(x, "*", yPlus1, x.position)
+                        return listOf(IAstModification.ReplaceNode(expr, newExpr, parent))
+                    }
+                }
+            }
+        }
+
+        if(expr.operator == ">=" && rightVal?.number == 0) {
+            if (leftDt == DataType.UBYTE || leftDt == DataType.UWORD) {
+                // unsigned >= 0 --> true
+                return listOf(IAstModification.ReplaceNode(expr, NumericLiteralValue.fromBoolean(true, expr.position), parent))
+            }
+            when(leftDt) {
+                DataType.BYTE -> {
+                    // signed >=0   --> signed ^ $80
+                    return listOf(IAstModification.ReplaceNode(
+                            expr,
+                            BinaryExpression(expr.left, "^", NumericLiteralValue.optimalInteger(0x80, expr.position), expr.position),
+                            parent
+                    ))
+                }
+                DataType.WORD -> {
+                    // signedw >=0   --> msb(signedw) ^ $80
+                    return listOf(IAstModification.ReplaceNode(
+                            expr,
+                            BinaryExpression(FunctionCall(IdentifierReference(listOf("msb"), expr.position),
+                                    mutableListOf(expr.left),
+                                    expr.position
+                            ), "^", NumericLiteralValue.optimalInteger(0x80, expr.position), expr.position),
+                            parent
+                    ))
+                }
+                else -> {}
+            }
+        }
+
+        if(expr.operator == "<" && rightVal?.number == 0) {
+            if (leftDt == DataType.UBYTE || leftDt == DataType.UWORD) {
+                // unsigned < 0 --> false
+                return listOf(IAstModification.ReplaceNode(expr, NumericLiteralValue.fromBoolean(false, expr.position), parent))
+            }
+            when(leftDt) {
+                DataType.BYTE -> {
+                    // signed < 0  -->  signed & $80
+                    return listOf(IAstModification.ReplaceNode(
+                            expr,
+                            BinaryExpression(expr.left, "&", NumericLiteralValue.optimalInteger(0x80, expr.position), expr.position),
+                            parent
+                    ))
+                }
+                DataType.WORD -> {
+                    // signedw < 0 -->  msb(signedw) & $80
+                    return listOf(IAstModification.ReplaceNode(
+                            expr,
+                            BinaryExpression(FunctionCall(IdentifierReference(listOf("msb"), expr.position),
+                                    mutableListOf(expr.left),
+                                    expr.position
+                            ), "&", NumericLiteralValue.optimalInteger(0x80, expr.position), expr.position),
+                            parent
+                    ))
+                }
+                else -> {}
+            }
+        }
+
+        // simplify when a term is constant and directly determines the outcome
+        val constTrue = NumericLiteralValue.fromBoolean(true, expr.position)
+        val constFalse = NumericLiteralValue.fromBoolean(false, expr.position)
+        val newExpr: Expression? = when (expr.operator) {
+            "or" -> {
+                if ((leftVal != null && leftVal.asBooleanValue) || (rightVal != null && rightVal.asBooleanValue))
+                    constTrue
+                else if (leftVal != null && !leftVal.asBooleanValue)
+                    expr.right
+                else if (rightVal != null && !rightVal.asBooleanValue)
+                    expr.left
+                else
+                    null
+            }
+            "and" -> {
+                if ((leftVal != null && !leftVal.asBooleanValue) || (rightVal != null && !rightVal.asBooleanValue))
+                    constFalse
+                else if (leftVal != null && leftVal.asBooleanValue)
+                    expr.right
+                else if (rightVal != null && rightVal.asBooleanValue)
+                    expr.left
+                else
+                    null
+            }
+            "xor" -> {
+                if (leftVal != null && !leftVal.asBooleanValue)
+                    expr.right
+                else if (rightVal != null && !rightVal.asBooleanValue)
+                    expr.left
+                else if (leftVal != null && leftVal.asBooleanValue)
+                    PrefixExpression("not", expr.right, expr.right.position)
+                else if (rightVal != null && rightVal.asBooleanValue)
+                    PrefixExpression("not", expr.left, expr.left.position)
+                else
+                    null
+            }
+            "|", "^" -> {
+                if (leftVal != null && !leftVal.asBooleanValue)
+                    expr.right
+                else if (rightVal != null && !rightVal.asBooleanValue)
+                    expr.left
+                else
+                    null
+            }
+            "&" -> {
+                if (leftVal != null && !leftVal.asBooleanValue)
+                    constFalse
+                else if (rightVal != null && !rightVal.asBooleanValue)
+                    constFalse
+                else
+                    null
+            }
+            "*" -> optimizeMultiplication(expr, leftVal, rightVal)
+            "/" -> optimizeDivision(expr, leftVal, rightVal)
+            "+" -> optimizeAdd(expr, leftVal, rightVal)
+            "-" -> optimizeSub(expr, leftVal, rightVal)
+            "**" -> optimizePower(expr, leftVal, rightVal)
+            "%" -> optimizeRemainder(expr, leftVal, rightVal)
+            ">>" -> optimizeShiftRight(expr, rightVal)
+            "<<" -> optimizeShiftLeft(expr, rightVal)
+            else -> null
+        }
+
+        if(newExpr != null)
+            return listOf(IAstModification.ReplaceNode(expr, newExpr, parent))
+
+        return noModifications
+    }
+
+    override fun after(functionCall: FunctionCall, parent: Node): Iterable<IAstModification> {
+        if(functionCall.target.nameInSource == listOf("lsb")) {
+            val arg = functionCall.args[0]
+            if(arg is TypecastExpression) {
+                val valueDt = arg.expression.inferType(program)
+                if (valueDt.istype(DataType.BYTE) || valueDt.istype(DataType.UBYTE)) {
+                    // useless lsb() of byte value that was casted to word
+                    return listOf(IAstModification.ReplaceNode(functionCall, arg.expression, parent))
+                }
+            } else {
+                val argDt = arg.inferType(program)
+                if (argDt.istype(DataType.BYTE) || argDt.istype(DataType.UBYTE)) {
+                    // useless lsb() of byte value
+                    return listOf(IAstModification.ReplaceNode(functionCall, arg, parent))
+                }
+            }
+        }
+        else if(functionCall.target.nameInSource == listOf("msb")) {
+            val arg = functionCall.args[0]
+            if(arg is TypecastExpression) {
+                val valueDt = arg.expression.inferType(program)
+                if (valueDt.istype(DataType.BYTE) || valueDt.istype(DataType.UBYTE)) {
+                    // useless msb() of byte value that was casted to word, replace with 0
+                    return listOf(IAstModification.ReplaceNode(
+                            functionCall,
+                            NumericLiteralValue(valueDt.typeOrElse(DataType.UBYTE), 0, arg.expression.position),
+                            parent))
+                }
+            } else {
+                val argDt = arg.inferType(program)
+                if (argDt.istype(DataType.BYTE) || argDt.istype(DataType.UBYTE)) {
+                    // useless msb() of byte value, replace with 0
+                    return listOf(IAstModification.ReplaceNode(
+                            functionCall,
+                            NumericLiteralValue(argDt.typeOrElse(DataType.UBYTE), 0, arg.position),
+                            parent))
+                }
+            }
+        }
+
+        return noModifications
+    }
+
+    private fun determineY(x: Expression, subBinExpr: BinaryExpression): Expression? {
+        return when {
+            subBinExpr.left isSameAs x -> subBinExpr.right
+            subBinExpr.right isSameAs x -> subBinExpr.left
+            else -> null
+        }
+    }
+
+    private fun optimizeAdd(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression? {
+        if(expr.left.isSameAs(expr.right)) {
+            // optimize X+X into X *2
+            expr.operator = "*"
+            expr.right = NumericLiteralValue.optimalInteger(2, expr.right.position)
+            expr.right.linkParents(expr)
+            return expr
+        }
+
+        if (leftVal == null && rightVal == null)
+            return null
+
+        val (expr2, _, rightVal2) = reorderAssociative(expr, leftVal)
+        if (rightVal2 != null) {
+            // right value is a constant, see if we can optimize
+            val rightConst: NumericLiteralValue = rightVal2
+            when (rightConst.number.toDouble()) {
+                0.0 -> {
+                    // left
+                    return expr2.left
+                }
+            }
+        }
+        // no need to check for left val constant (because of associativity)
+
+        return null
+    }
+
+    private fun optimizeSub(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression? {
+        if(expr.left.isSameAs(expr.right)) {
+            // optimize X-X into 0
+            return NumericLiteralValue.optimalInteger(0, expr.position)
+        }
+
+        if (leftVal == null && rightVal == null)
+            return null
+
+        if (rightVal != null) {
+            // right value is a constant, see if we can optimize
+            val rightConst: NumericLiteralValue = rightVal
+            when (rightConst.number.toDouble()) {
+                0.0 -> {
+                    // left
+                    return expr.left
+                }
+            }
+        }
+        if (leftVal != null) {
+            // left value is a constant, see if we can optimize
+            when (leftVal.number.toDouble()) {
+                0.0 -> {
+                    // -right
+                    return PrefixExpression("-", expr.right, expr.position)
+                }
+            }
+        }
+
+        return null
+    }
+
+    private fun optimizePower(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression? {
+        if (leftVal == null && rightVal == null)
+            return null
+
+        if (rightVal != null) {
+            // right value is a constant, see if we can optimize
+            val rightConst: NumericLiteralValue = rightVal
+            when (rightConst.number.toDouble()) {
+                -3.0 -> {
+                    // -1/(left*left*left)
+                    return BinaryExpression(NumericLiteralValue(DataType.FLOAT, -1.0, expr.position), "/",
+                            BinaryExpression(expr.left, "*", BinaryExpression(expr.left, "*", expr.left, expr.position), expr.position),
+                            expr.position)
+                }
+                -2.0 -> {
+                    // -1/(left*left)
+                    return BinaryExpression(NumericLiteralValue(DataType.FLOAT, -1.0, expr.position), "/",
+                            BinaryExpression(expr.left, "*", expr.left, expr.position),
+                            expr.position)
+                }
+                -1.0 -> {
+                    // -1/left
+                    return BinaryExpression(NumericLiteralValue(DataType.FLOAT, -1.0, expr.position), "/",
+                            expr.left, expr.position)
+                }
+                0.0 -> {
+                    // 1
+                    return NumericLiteralValue(rightConst.type, 1, expr.position)
+                }
+                0.5 -> {
+                    // sqrt(left)
+                    return FunctionCall(IdentifierReference(listOf("sqrt"), expr.position), mutableListOf(expr.left), expr.position)
+                }
+                1.0 -> {
+                    // left
+                    return expr.left
+                }
+                2.0 -> {
+                    // left*left
+                    return BinaryExpression(expr.left, "*", expr.left, expr.position)
+                }
+                3.0 -> {
+                    // left*left*left
+                    return BinaryExpression(expr.left, "*", BinaryExpression(expr.left, "*", expr.left, expr.position), expr.position)
+                }
+            }
+        }
+        if (leftVal != null) {
+            // left value is a constant, see if we can optimize
+            when (leftVal.number.toDouble()) {
+                -1.0 -> {
+                    // -1
+                    return NumericLiteralValue(DataType.FLOAT, -1.0, expr.position)
+                }
+                0.0 -> {
+                    // 0
+                    return NumericLiteralValue(leftVal.type, 0, expr.position)
+                }
+                1.0 -> {
+                    //1
+                    return NumericLiteralValue(leftVal.type, 1, expr.position)
+                }
+
+            }
+        }
+
+        return null
+    }
+
+    private fun optimizeRemainder(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression? {
+        if (leftVal == null && rightVal == null)
+            return null
+
+        // simplify assignments  A = B <operator> C
+
+        val cv = rightVal?.number?.toInt()?.toDouble()
+        when (expr.operator) {
+            "%" -> {
+                if (cv == 1.0) {
+                    return NumericLiteralValue(expr.inferType(program).typeOrElse(DataType.STRUCT), 0, expr.position)
+                } else if (cv == 2.0) {
+                    expr.operator = "&"
+                    expr.right = NumericLiteralValue.optimalInteger(1, expr.position)
+                    return null
+                }
+            }
+        }
+        return null
+
+    }
+
+    private fun optimizeDivision(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression? {
+        if (leftVal == null && rightVal == null)
+            return null
+
+        // cannot shuffle assiciativity with division!
+        if (rightVal != null) {
+            // right value is a constant, see if we can optimize
+            val rightConst: NumericLiteralValue = rightVal
+            val cv = rightConst.number.toDouble()
+            val leftIDt = expr.left.inferType(program)
+            if (!leftIDt.isKnown)
+                return null
+            val leftDt = leftIDt.typeOrElse(DataType.STRUCT)
+            when (cv) {
+                -1.0 -> {
+                    //  '/' -> -left
+                    if (expr.operator == "/") {
+                        return PrefixExpression("-", expr.left, expr.position)
+                    }
+                }
+                1.0 -> {
+                    //  '/' -> left
+                    if (expr.operator == "/") {
+                        return expr.left
+                    }
+                }
+                in powersOfTwo -> {
+                    if (leftDt in IntegerDatatypes) {
+                        // divided by a power of two => shift right
+                        val numshifts = log2(cv).toInt()
+                        return BinaryExpression(expr.left, ">>", NumericLiteralValue.optimalInteger(numshifts, expr.position), expr.position)
+                    }
+                }
+                in negativePowersOfTwo -> {
+                    if (leftDt in IntegerDatatypes) {
+                        // divided by a negative power of two => negate, then shift right
+                        val numshifts = log2(-cv).toInt()
+                        return BinaryExpression(PrefixExpression("-", expr.left, expr.position), ">>", NumericLiteralValue.optimalInteger(numshifts, expr.position), expr.position)
+                    }
+                }
+            }
+
+            if (leftDt == DataType.UBYTE) {
+                if (abs(rightConst.number.toDouble()) >= 256.0) {
+                    return NumericLiteralValue(DataType.UBYTE, 0, expr.position)
+                }
+            } else if (leftDt == DataType.UWORD) {
+                if (abs(rightConst.number.toDouble()) >= 65536.0) {
+                    return NumericLiteralValue(DataType.UBYTE, 0, expr.position)
+                }
+            }
+        }
+
+        if (leftVal != null) {
+            // left value is a constant, see if we can optimize
+            when (leftVal.number.toDouble()) {
+                0.0 -> {
+                    // 0
+                    return NumericLiteralValue(leftVal.type, 0, expr.position)
+                }
+            }
+        }
+
+        return null
+    }
+
+    private fun optimizeMultiplication(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression? {
+        if (leftVal == null && rightVal == null)
+            return null
+
+        val (expr2, _, rightVal2) = reorderAssociative(expr, leftVal)
+        if (rightVal2 != null) {
+            // right value is a constant, see if we can optimize
+            val leftValue: Expression = expr2.left
+            val rightConst: NumericLiteralValue = rightVal2
+            when (val cv = rightConst.number.toDouble()) {
+                -1.0 -> {
+                    // -left
+                    return PrefixExpression("-", leftValue, expr.position)
+                }
+                0.0 -> {
+                    // 0
+                    return NumericLiteralValue(rightConst.type, 0, expr.position)
+                }
+                1.0 -> {
+                    // left
+                    return expr2.left
+                }
+                in powersOfTwo -> {
+                    if (leftValue.inferType(program).typeOrElse(DataType.STRUCT) in IntegerDatatypes) {
+                        // times a power of two => shift left
+                        val numshifts = log2(cv).toInt()
+                        return BinaryExpression(expr2.left, "<<", NumericLiteralValue.optimalInteger(numshifts, expr.position), expr.position)
+                    }
+                }
+                in negativePowersOfTwo -> {
+                    if (leftValue.inferType(program).typeOrElse(DataType.STRUCT) in IntegerDatatypes) {
+                        // times a negative power of two => negate, then shift left
+                        val numshifts = log2(-cv).toInt()
+                        return BinaryExpression(PrefixExpression("-", expr2.left, expr.position), "<<", NumericLiteralValue.optimalInteger(numshifts, expr.position), expr.position)
+                    }
+                }
+            }
+        }
+        // no need to check for left val constant (because of associativity)
+
+        return null
+    }
+
+    private fun optimizeShiftLeft(expr: BinaryExpression, amountLv: NumericLiteralValue?): Expression? {
+        if (amountLv == null)
+            return null
+
+        val amount = amountLv.number.toInt()
+        if (amount == 0) {
+            return expr.left
+        }
+        val targetDt = expr.left.inferType(program).typeOrElse(DataType.STRUCT)
+        when (targetDt) {
+            DataType.UBYTE, DataType.BYTE -> {
+                if (amount >= 8) {
+                    return NumericLiteralValue(targetDt, 0, expr.position)
+                }
+            }
+            DataType.UWORD, DataType.WORD -> {
+                if (amount >= 16) {
+                    return NumericLiteralValue(targetDt, 0, expr.position)
+                } else if (amount >= 8) {
+                    val lsb = TypecastExpression(expr.left, DataType.UBYTE, true, expr.position)
+                    if (amount == 8) {
+                        return FunctionCall(IdentifierReference(listOf("mkword"), expr.position), mutableListOf(lsb, NumericLiteralValue.optimalInteger(0, expr.position)), expr.position)
+                    }
+                    val shifted = BinaryExpression(lsb, "<<", NumericLiteralValue.optimalInteger(amount - 8, expr.position), expr.position)
+                    return FunctionCall(IdentifierReference(listOf("mkword"), expr.position), mutableListOf(shifted, NumericLiteralValue.optimalInteger(0, expr.position)), expr.position)
+                }
+            }
+            else -> {
+            }
+        }
+        return null
+    }
+
+    private fun optimizeShiftRight(expr: BinaryExpression, amountLv: NumericLiteralValue?): Expression? {
+        if (amountLv == null)
+            return null
+
+        val amount = amountLv.number.toInt()
+        if (amount == 0) {
+            return expr.left
+        }
+        when (expr.left.inferType(program).typeOrElse(DataType.STRUCT)) {
+            DataType.UBYTE -> {
+                if (amount >= 8) {
+                    return NumericLiteralValue.optimalInteger(0, expr.position)
+                }
+            }
+            DataType.BYTE -> {
+                if (amount > 8) {
+                    expr.right = NumericLiteralValue.optimalInteger(8, expr.right.position)
+                    return null
+                }
+            }
+            DataType.UWORD -> {
+                if (amount >= 16) {
+                    return NumericLiteralValue.optimalInteger(0, expr.position)
+                } else if (amount >= 8) {
+                    val msb = FunctionCall(IdentifierReference(listOf("msb"), expr.position), mutableListOf(expr.left), expr.position)
+                    if (amount == 8)
+                        return msb
+                    return BinaryExpression(msb, ">>", NumericLiteralValue.optimalInteger(amount - 8, expr.position), expr.position)
+                }
+            }
+            DataType.WORD -> {
+                if (amount > 16) {
+                    expr.right = NumericLiteralValue.optimalInteger(16, expr.right.position)
+                    return null
+                } else if (amount >= 8) {
+                    val msbAsByte = TypecastExpression(
+                            FunctionCall(IdentifierReference(listOf("msb"), expr.position), mutableListOf(expr.left), expr.position),
+                            DataType.BYTE,
+                            true, expr.position)
+                    if (amount == 8)
+                        return msbAsByte
+                    return BinaryExpression(msbAsByte, ">>", NumericLiteralValue.optimalInteger(amount - 8, expr.position), expr.position)
+                }
+            }
+            else -> {
+            }
+        }
+        return null
+    }
+
+    private fun reorderAssociative(expr: BinaryExpression, leftVal: NumericLiteralValue?): ReorderedAssociativeBinaryExpr {
+        if (expr.operator in associativeOperators && leftVal != null) {
+            // swap left and right so that right is always the constant
+            val tmp = expr.left
+            expr.left = expr.right
+            expr.right = tmp
+            return ReorderedAssociativeBinaryExpr(expr, expr.right.constValue(program), leftVal)
+        }
+        return ReorderedAssociativeBinaryExpr(expr, leftVal, expr.right.constValue(program))
+    }
+
+    private data class ReorderedAssociativeBinaryExpr(val expr: BinaryExpression, val leftVal: NumericLiteralValue?, val rightVal: NumericLiteralValue?)
+
+}
@@ -5,12 +5,32 @@ import prog8.ast.base.ErrorReporter


 internal fun Program.constantFold(errors: ErrorReporter) {
-    val optimizer = ConstantFolding(this, errors)
-    optimizer.visit(this)
+    val valuetypefixer = VarConstantValueTypeAdjuster(this, errors)
+    valuetypefixer.visit(this)
+    if(errors.isEmpty()) {
+        valuetypefixer.applyModifications()

-    while(errors.isEmpty() && optimizer.optimizationsDone>0) {
-        optimizer.optimizationsDone = 0
-        optimizer.visit(this)
+        val replacer = ConstantIdentifierReplacer(this, errors)
+        replacer.visit(this)
+        if (errors.isEmpty()) {
+            replacer.applyModifications()
+
+            valuetypefixer.visit(this)
+            if(errors.isEmpty()) {
+                valuetypefixer.applyModifications()
+
+                val optimizer = ConstantFoldingOptimizer(this)
+                optimizer.visit(this)
+                while (errors.isEmpty() && optimizer.applyModifications() > 0) {
+                    optimizer.visit(this)
+                }
+
+                if (errors.isEmpty()) {
+                    replacer.visit(this)
+                    replacer.applyModifications()
+                }
+            }
+        }
    }

    if(errors.isEmpty())
@@ -21,13 +41,15 @@ internal fun Program.constantFold(errors: ErrorReporter) {
 internal fun Program.optimizeStatements(errors: ErrorReporter): Int {
    val optimizer = StatementOptimizer(this, errors)
    optimizer.visit(this)
+    val optimizationCount = optimizer.applyModifications()
+
    modules.forEach { it.linkParents(this.namespace) }   // re-link in final configuration

-    return optimizer.optimizationsDone
+    return optimizationCount
 }

 internal fun Program.simplifyExpressions() : Int {
-    val optimizer = SimplifyExpressions(this)
-    optimizer.visit(this)
-    return optimizer.optimizationsDone
+    val opti = ExpressionSimplifier(this)
+    opti.visit(this)
+    return opti.applyModifications()
 }
@@ -1,828 +0,0 @@
-package prog8.optimizer
-
-import prog8.ast.Program
-import prog8.ast.base.*
-import prog8.ast.expressions.*
-import prog8.ast.processing.IAstModifyingVisitor
-import prog8.ast.statements.Assignment
-import prog8.ast.statements.Statement
-import kotlin.math.abs
-import kotlin.math.log2
-import kotlin.math.pow
-
-/*
-    todo add more expression optimizations
-
-    Investigate what optimizations binaryen has, also see  https://egorbo.com/peephole-optimizations.html
-
- */
-
-internal class SimplifyExpressions(private val program: Program) : IAstModifyingVisitor {
-    var optimizationsDone: Int = 0
-
-    override fun visit(assignment: Assignment): Statement {
-        if (assignment.aug_op != null)
-            throw AstException("augmented assignments should have been converted to normal assignments before this optimizer: $assignment")
-        return super.visit(assignment)
-    }
-
-    override fun visit(memread: DirectMemoryRead): Expression {
-        // @( &thing )  -->  thing
-        val addrOf = memread.addressExpression as? AddressOf
-        if(addrOf!=null)
-            return super.visit(addrOf.identifier)
-        return super.visit(memread)
-    }
-
-    override fun visit(typecast: TypecastExpression): Expression {
-        var tc = typecast
-
-        // try to statically convert a literal value into one of the desired type
-        val literal = tc.expression as? NumericLiteralValue
-        if(literal!=null) {
-            val newLiteral = literal.cast(tc.type)
-            if(newLiteral!==literal) {
-                optimizationsDone++
-                return newLiteral
-            }
-        }
-
-        // remove redundant typecasts
-        while(true) {
-            val expr = tc.expression
-            if(expr !is TypecastExpression || expr.type!=tc.type) {
-                val assignment = typecast.parent as? Assignment
-                if(assignment!=null) {
-                    val targetDt = assignment.target.inferType(program, assignment)
-                    if(tc.expression.inferType(program)==targetDt) {
-                        optimizationsDone++
-                        return tc.expression
-                    }
-                }
-
-                val subTc = tc.expression as? TypecastExpression
-                if(subTc!=null) {
-                    // if the previous typecast was casting to a 'bigger' type, just ignore that one
-                    // if the previous typecast was casting to a similar type, ignore that one
-                    if(subTc.type largerThan tc.type || subTc.type equalsSize tc.type) {
-                        subTc.type = tc.type
-                        subTc.parent = tc.parent
-                        optimizationsDone++
-                        return subTc
-                    }
-                }
-
-                return super.visit(tc)
-            }
-
-            optimizationsDone++
-            tc = expr
-        }
-    }
-
-    override fun visit(expr: PrefixExpression): Expression {
-        if (expr.operator == "+") {
-            // +X --> X
-            optimizationsDone++
-            return expr.expression.accept(this)
-        } else if (expr.operator == "not") {
-            (expr.expression as? BinaryExpression)?.let {
-                // NOT (...)  ->   invert  ...
-                when (it.operator) {
-                    "<" -> {
-                        it.operator = ">="
-                        optimizationsDone++
-                        return it
-                    }
-                    ">" -> {
-                        it.operator = "<="
-                        optimizationsDone++
-                        return it
-                    }
-                    "<=" -> {
-                        it.operator = ">"
-                        optimizationsDone++
-                        return it
-                    }
-                    ">=" -> {
-                        it.operator = "<"
-                        optimizationsDone++
-                        return it
-                    }
-                    "==" -> {
-                        it.operator = "!="
-                        optimizationsDone++
-                        return it
-                    }
-                    "!=" -> {
-                        it.operator = "=="
-                        optimizationsDone++
-                        return it
-                    }
-                    else -> {
-                    }
-                }
-            }
-        }
-        return super.visit(expr)
-    }
-
-    override fun visit(expr: BinaryExpression): Expression {
-        super.visit(expr)
-        val leftVal = expr.left.constValue(program)
-        val rightVal = expr.right.constValue(program)
-        val constTrue = NumericLiteralValue.fromBoolean(true, expr.position)
-        val constFalse = NumericLiteralValue.fromBoolean(false, expr.position)
-
-        val leftIDt = expr.left.inferType(program)
-        val rightIDt = expr.right.inferType(program)
-        if(!leftIDt.isKnown || !rightIDt.isKnown)
-            throw FatalAstException("can't determine datatype of both expression operands $expr")
-
-        val leftDt = leftIDt.typeOrElse(DataType.STRUCT)
-        val rightDt = rightIDt.typeOrElse(DataType.STRUCT)
-        if (leftDt != rightDt) {
-            // try to convert a datatype into the other (where ddd
-            if (adjustDatatypes(expr, leftVal, leftDt, rightVal, rightDt)) {
-                optimizationsDone++
-                return expr
-            }
-        }
-
-        // Value <associativeoperator> X -->  X <associativeoperator> Value
-        if (leftVal != null && expr.operator in associativeOperators && rightVal == null) {
-            val tmp = expr.left
-            expr.left = expr.right
-            expr.right = tmp
-            optimizationsDone++
-            return expr
-        }
-
-        // X + (-A)  -->  X - A
-        if (expr.operator == "+" && (expr.right as? PrefixExpression)?.operator == "-") {
-            expr.operator = "-"
-            expr.right = (expr.right as PrefixExpression).expression
-            optimizationsDone++
-            return expr
-        }
-
-        // (-A) + X  -->  X - A
-        if (expr.operator == "+" && (expr.left as? PrefixExpression)?.operator == "-") {
-            expr.operator = "-"
-            val newRight = (expr.left as PrefixExpression).expression
-            expr.left = expr.right
-            expr.right = newRight
-            optimizationsDone++
-            return expr
-        }
-
-        // X + (-value)  -->  X - value
-        if (expr.operator == "+" && rightVal != null) {
-            val rv = rightVal.number.toDouble()
-            if (rv < 0.0) {
-                expr.operator = "-"
-                expr.right = NumericLiteralValue(rightVal.type, -rv, rightVal.position)
-                optimizationsDone++
-                return expr
-            }
-        }
-
-        // (-value) + X  -->  X - value
-        if (expr.operator == "+" && leftVal != null) {
-            val lv = leftVal.number.toDouble()
-            if (lv < 0.0) {
-                expr.operator = "-"
-                expr.right = NumericLiteralValue(leftVal.type, -lv, leftVal.position)
-                optimizationsDone++
-                return expr
-            }
-        }
-
-        // X - (-A)  -->  X + A
-        if (expr.operator == "-" && (expr.right as? PrefixExpression)?.operator == "-") {
-            expr.operator = "+"
-            expr.right = (expr.right as PrefixExpression).expression
-            optimizationsDone++
-            return expr
-        }
-
-        // X - (-value)  -->  X + value
-        if (expr.operator == "-" && rightVal != null) {
-            val rv = rightVal.number.toDouble()
-            if (rv < 0.0) {
-                expr.operator = "+"
-                expr.right = NumericLiteralValue(rightVal.type, -rv, rightVal.position)
-                optimizationsDone++
-                return expr
-            }
-        }
-
-        if (expr.operator == "+" || expr.operator == "-"
-                && leftVal == null && rightVal == null
-                && leftDt in NumericDatatypes && rightDt in NumericDatatypes) {
-            val leftBinExpr = expr.left as? BinaryExpression
-            val rightBinExpr = expr.right as? BinaryExpression
-            if (leftBinExpr?.operator == "*") {
-                if (expr.operator == "+") {
-                    // Y*X + X  ->  X*(Y - 1)
-                    // X*Y + X  ->  X*(Y - 1)
-                    val x = expr.right
-                    val y = determineY(x, leftBinExpr)
-                    if(y!=null) {
-                        val yPlus1 = BinaryExpression(y, "+", NumericLiteralValue(leftDt, 1, y.position), y.position)
-                        return BinaryExpression(x, "*", yPlus1, x.position)
-                    }
-                } else {
-                    // Y*X - X  ->  X*(Y - 1)
-                    // X*Y - X  ->  X*(Y - 1)
-                    val x = expr.right
-                    val y = determineY(x, leftBinExpr)
-                    if(y!=null) {
-                        val yMinus1 = BinaryExpression(y, "-", NumericLiteralValue(leftDt, 1, y.position), y.position)
-                        return BinaryExpression(x, "*", yMinus1, x.position)
-                    }
-                }
-            }
-            else if(rightBinExpr?.operator=="*") {
-                if(expr.operator=="+") {
-                    // X + Y*X  ->  X*(Y + 1)
-                    // X + X*Y  ->  X*(Y + 1)
-                    val x = expr.left
-                    val y = determineY(x, rightBinExpr)
-                    if(y!=null) {
-                        val yPlus1 = BinaryExpression(y, "+", NumericLiteralValue.optimalInteger(1, y.position), y.position)
-                        return BinaryExpression(x, "*", yPlus1, x.position)
-                    }
-                } else {
-                    // X - Y*X  ->  X*(1 - Y)
-                    // X - X*Y  ->  X*(1 - Y)
-                    val x = expr.left
-                    val y = determineY(x, rightBinExpr)
-                    if(y!=null) {
-                        val oneMinusY = BinaryExpression(NumericLiteralValue.optimalInteger(1, y.position), "-", y, y.position)
-                        return BinaryExpression(x, "*", oneMinusY, x.position)
-                    }
-                }
-            }
-        }
-
-
-        // simplify when a term is constant and determines the outcome
-        when (expr.operator) {
-            "or" -> {
-                if ((leftVal != null && leftVal.asBooleanValue) || (rightVal != null && rightVal.asBooleanValue)) {
-                    optimizationsDone++
-                    return constTrue
-                }
-                if (leftVal != null && !leftVal.asBooleanValue) {
-                    optimizationsDone++
-                    return expr.right
-                }
-                if (rightVal != null && !rightVal.asBooleanValue) {
-                    optimizationsDone++
-                    return expr.left
-                }
-            }
-            "and" -> {
-                if ((leftVal != null && !leftVal.asBooleanValue) || (rightVal != null && !rightVal.asBooleanValue)) {
-                    optimizationsDone++
-                    return constFalse
-                }
-                if (leftVal != null && leftVal.asBooleanValue) {
-                    optimizationsDone++
-                    return expr.right
-                }
-                if (rightVal != null && rightVal.asBooleanValue) {
-                    optimizationsDone++
-                    return expr.left
-                }
-            }
-            "xor" -> {
-                if (leftVal != null && !leftVal.asBooleanValue) {
-                    optimizationsDone++
-                    return expr.right
-                }
-                if (rightVal != null && !rightVal.asBooleanValue) {
-                    optimizationsDone++
-                    return expr.left
-                }
-                if (leftVal != null && leftVal.asBooleanValue) {
-                    optimizationsDone++
-                    return PrefixExpression("not", expr.right, expr.right.position)
-                }
-                if (rightVal != null && rightVal.asBooleanValue) {
-                    optimizationsDone++
-                    return PrefixExpression("not", expr.left, expr.left.position)
-                }
-            }
-            "|", "^" -> {
-                if (leftVal != null && !leftVal.asBooleanValue) {
-                    optimizationsDone++
-                    return expr.right
-                }
-                if (rightVal != null && !rightVal.asBooleanValue) {
-                    optimizationsDone++
-                    return expr.left
-                }
-            }
-            "&" -> {
-                if (leftVal != null && !leftVal.asBooleanValue) {
-                    optimizationsDone++
-                    return constFalse
-                }
-                if (rightVal != null && !rightVal.asBooleanValue) {
-                    optimizationsDone++
-                    return constFalse
-                }
-            }
-            "*" -> return optimizeMultiplication(expr, leftVal, rightVal)
-            "/" -> return optimizeDivision(expr, leftVal, rightVal)
-            "+" -> return optimizeAdd(expr, leftVal, rightVal)
-            "-" -> return optimizeSub(expr, leftVal, rightVal)
-            "**" -> return optimizePower(expr, leftVal, rightVal)
-            "%" -> return optimizeRemainder(expr, leftVal, rightVal)
-            ">>" -> return optimizeShiftRight(expr, rightVal)
-            "<<" -> return optimizeShiftLeft(expr, rightVal)
-        }
-        return expr
-    }
-
-    private fun determineY(x: Expression, subBinExpr: BinaryExpression): Expression? {
-        return when {
-            subBinExpr.left isSameAs x -> subBinExpr.right
-            subBinExpr.right isSameAs x -> subBinExpr.left
-            else -> null
-        }
-    }
-
-    private fun adjustDatatypes(expr: BinaryExpression,
-                                leftConstVal: NumericLiteralValue?, leftDt: DataType,
-                                rightConstVal: NumericLiteralValue?, rightDt: DataType): Boolean {
-
-        fun adjust(value: NumericLiteralValue, targetDt: DataType): Pair<Boolean, NumericLiteralValue>{
-            if(value.type==targetDt)
-                return Pair(false, value)
-            when(value.type) {
-                DataType.UBYTE -> {
-                    if (targetDt == DataType.BYTE) {
-                        if(value.number.toInt() < 127)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toShort(), value.position))
-                    }
-                    else if (targetDt == DataType.UWORD || targetDt == DataType.WORD)
-                        return Pair(true, NumericLiteralValue(targetDt, value.number.toInt(), value.position))
-                }
-                DataType.BYTE -> {
-                    if (targetDt == DataType.UBYTE) {
-                        if(value.number.toInt() >= 0)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toInt(), value.position))
-                    }
-                    else if (targetDt == DataType.UWORD) {
-                        if(value.number.toInt() >= 0)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toInt(), value.position))
-                    }
-                    else if (targetDt == DataType.WORD) return Pair(true, NumericLiteralValue(targetDt, value.number.toInt(), value.position))
-                }
-                DataType.UWORD -> {
-                    if (targetDt == DataType.UBYTE) {
-                        if(value.number.toInt() <= 255)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toShort(), value.position))
-                    }
-                    else if (targetDt == DataType.BYTE) {
-                        if(value.number.toInt() <= 127)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toShort(), value.position))
-                    }
-                    else if (targetDt == DataType.WORD) {
-                        if(value.number.toInt() <= 32767)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toInt(), value.position))
-                    }
-                }
-                DataType.WORD -> {
-                    if (targetDt == DataType.UBYTE) {
-                        if(value.number.toInt() in 0..255)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toShort(), value.position))
-                    }
-                    else if (targetDt == DataType.BYTE) {
-                        if(value.number.toInt() in -128..127)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toShort(), value.position))
-                    }
-                    else if (targetDt == DataType.UWORD) {
-                        if(value.number.toInt() >= 0)
-                            return Pair(true, NumericLiteralValue(targetDt, value.number.toShort(), value.position))
-                    }
-                }
-                else -> {}
-            }
-            return Pair(false, value)
-        }
-
-        if(leftConstVal==null && rightConstVal!=null) {
-            if(leftDt largerThan rightDt) {
-                val (adjusted, newValue) = adjust(rightConstVal, leftDt)
-                if (adjusted) {
-                    expr.right = newValue
-                    optimizationsDone++
-                    return true
-                }
-            }
-            return false
-        } else if(leftConstVal!=null && rightConstVal==null) {
-            if(rightDt largerThan leftDt) {
-                val (adjusted, newValue) = adjust(leftConstVal, rightDt)
-                if (adjusted) {
-                    expr.left = newValue
-                    optimizationsDone++
-                    return true
-                }
-            }
-            return false
-        } else {
-            return false    // two const values, don't adjust (should have been const-folded away)
-        }
-    }
-
-    private data class ReorderedAssociativeBinaryExpr(val expr: BinaryExpression, val leftVal: NumericLiteralValue?, val rightVal: NumericLiteralValue?)
-
-    private fun reorderAssociative(expr: BinaryExpression, leftVal: NumericLiteralValue?): ReorderedAssociativeBinaryExpr {
-        if(expr.operator in associativeOperators && leftVal!=null) {
-            // swap left and right so that right is always the constant
-            val tmp = expr.left
-            expr.left = expr.right
-            expr.right = tmp
-            optimizationsDone++
-            return ReorderedAssociativeBinaryExpr(expr, expr.right.constValue(program), leftVal)
-        }
-        return ReorderedAssociativeBinaryExpr(expr, leftVal, expr.right.constValue(program))
-    }
-
-    private fun optimizeAdd(pexpr: BinaryExpression, pleftVal: NumericLiteralValue?, prightVal: NumericLiteralValue?): Expression {
-        if(pleftVal==null && prightVal==null)
-            return pexpr
-
-        val (expr, _, rightVal) = reorderAssociative(pexpr, pleftVal)
-        if(rightVal!=null) {
-            // right value is a constant, see if we can optimize
-            val rightConst: NumericLiteralValue = rightVal
-            when(rightConst.number.toDouble()) {
-                0.0 -> {
-                    // left
-                    optimizationsDone++
-                    return expr.left
-                }
-            }
-        }
-        // no need to check for left val constant (because of associativity)
-
-        return expr
-    }
-
-    private fun optimizeSub(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression {
-        if(leftVal==null && rightVal==null)
-            return expr
-
-        if(rightVal!=null) {
-            // right value is a constant, see if we can optimize
-            val rightConst: NumericLiteralValue = rightVal
-            when(rightConst.number.toDouble()) {
-                0.0 -> {
-                    // left
-                    optimizationsDone++
-                    return expr.left
-                }
-            }
-        }
-        if(leftVal!=null) {
-            // left value is a constant, see if we can optimize
-            when(leftVal.number.toDouble()) {
-                0.0 -> {
-                    // -right
-                    optimizationsDone++
-                    return PrefixExpression("-", expr.right, expr.position)
-                }
-            }
-        }
-
-        return expr
-    }
-
-    private fun optimizePower(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression {
-        if(leftVal==null && rightVal==null)
-            return expr
-
-        if(rightVal!=null) {
-            // right value is a constant, see if we can optimize
-            val rightConst: NumericLiteralValue = rightVal
-            when(rightConst.number.toDouble()) {
-                -3.0 -> {
-                    // -1/(left*left*left)
-                    optimizationsDone++
-                    return BinaryExpression(NumericLiteralValue(DataType.FLOAT, -1.0, expr.position), "/",
-                            BinaryExpression(expr.left, "*", BinaryExpression(expr.left, "*", expr.left, expr.position), expr.position),
-                            expr.position)
-                }
-                -2.0 -> {
-                    // -1/(left*left)
-                    optimizationsDone++
-                    return BinaryExpression(NumericLiteralValue(DataType.FLOAT, -1.0, expr.position), "/",
-                            BinaryExpression(expr.left, "*", expr.left, expr.position),
-                            expr.position)
-                }
-                -1.0 -> {
-                    // -1/left
-                    optimizationsDone++
-                    return BinaryExpression(NumericLiteralValue(DataType.FLOAT, -1.0, expr.position), "/",
-                            expr.left, expr.position)
-                }
-                0.0 -> {
-                    // 1
-                    optimizationsDone++
-                    return NumericLiteralValue(rightConst.type, 1, expr.position)
-                }
-                0.5 -> {
-                    // sqrt(left)
-                    optimizationsDone++
-                    return FunctionCall(IdentifierReference(listOf("sqrt"), expr.position), mutableListOf(expr.left), expr.position)
-                }
-                1.0 -> {
-                    // left
-                    optimizationsDone++
-                    return expr.left
-                }
-                2.0 -> {
-                    // left*left
-                    optimizationsDone++
-                    return BinaryExpression(expr.left, "*", expr.left, expr.position)
-                }
-                3.0 -> {
-                    // left*left*left
-                    optimizationsDone++
-                    return BinaryExpression(expr.left, "*", BinaryExpression(expr.left, "*", expr.left, expr.position), expr.position)
-                }
-            }
-        }
-        if(leftVal!=null) {
-            // left value is a constant, see if we can optimize
-            when(leftVal.number.toDouble()) {
-                -1.0 -> {
-                    // -1
-                    optimizationsDone++
-                    return NumericLiteralValue(DataType.FLOAT, -1.0, expr.position)
-                }
-                0.0 -> {
-                    // 0
-                    optimizationsDone++
-                    return NumericLiteralValue(leftVal.type, 0, expr.position)
-                }
-                1.0 -> {
-                    //1
-                    optimizationsDone++
-                    return NumericLiteralValue(leftVal.type, 1, expr.position)
-                }
-
-            }
-        }
-
-        return expr
-    }
-
-    private fun optimizeRemainder(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression {
-        if(leftVal==null && rightVal==null)
-            return expr
-
-        // simplify assignments  A = B <operator> C
-
-        val cv = rightVal?.number?.toInt()?.toDouble()
-        when(expr.operator) {
-            "%" -> {
-                if (cv == 1.0) {
-                    optimizationsDone++
-                    return NumericLiteralValue(expr.inferType(program).typeOrElse(DataType.STRUCT), 0, expr.position)
-                } else if (cv == 2.0) {
-                    optimizationsDone++
-                    expr.operator = "&"
-                    expr.right = NumericLiteralValue.optimalInteger(1, expr.position)
-                    return expr
-                }
-            }
-        }
-        return expr
-
-    }
-
-    private val powersOfTwo = (1 .. 16).map { (2.0).pow(it) }.toSet()
-    private val negativePowersOfTwo = powersOfTwo.map { -it }.toSet()
-
-    private fun optimizeDivision(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression {
-        if(leftVal==null && rightVal==null)
-            return expr
-
-        // cannot shuffle assiciativity with division!
-        if(rightVal!=null) {
-            // right value is a constant, see if we can optimize
-            val rightConst: NumericLiteralValue = rightVal
-            val cv = rightConst.number.toDouble()
-            val leftIDt = expr.left.inferType(program)
-            if(!leftIDt.isKnown)
-                return expr
-            val leftDt = leftIDt.typeOrElse(DataType.STRUCT)
-            when(cv) {
-                -1.0 -> {
-                    //  '/' -> -left
-                    if (expr.operator == "/") {
-                        optimizationsDone++
-                        return PrefixExpression("-", expr.left, expr.position)
-                    }
-                }
-                1.0 -> {
-                    //  '/' -> left
-                    if (expr.operator == "/") {
-                        optimizationsDone++
-                        return expr.left
-                    }
-                }
-                in powersOfTwo -> {
-                    if(leftDt in IntegerDatatypes) {
-                        // divided by a power of two => shift right
-                        optimizationsDone++
-                        val numshifts = log2(cv).toInt()
-                        return BinaryExpression(expr.left, ">>", NumericLiteralValue.optimalInteger(numshifts, expr.position), expr.position)
-                    }
-                }
-                in negativePowersOfTwo -> {
-                    if(leftDt in IntegerDatatypes) {
-                        // divided by a negative power of two => negate, then shift right
-                        optimizationsDone++
-                        val numshifts = log2(-cv).toInt()
-                        return BinaryExpression(PrefixExpression("-", expr.left, expr.position), ">>", NumericLiteralValue.optimalInteger(numshifts, expr.position), expr.position)
-                    }
-                }
-            }
-
-            if (leftDt == DataType.UBYTE) {
-                if(abs(rightConst.number.toDouble()) >= 256.0) {
-                    optimizationsDone++
-                    return NumericLiteralValue(DataType.UBYTE, 0, expr.position)
-                }
-            }
-            else if (leftDt == DataType.UWORD) {
-                if(abs(rightConst.number.toDouble()) >= 65536.0) {
-                    optimizationsDone++
-                    return NumericLiteralValue(DataType.UBYTE, 0, expr.position)
-                }
-            }
-        }
-
-        if(leftVal!=null) {
-            // left value is a constant, see if we can optimize
-            when(leftVal.number.toDouble()) {
-                0.0 -> {
-                    // 0
-                    optimizationsDone++
-                    return NumericLiteralValue(leftVal.type, 0, expr.position)
-                }
-            }
-        }
-
-        return expr
-    }
-
-    private fun optimizeMultiplication(pexpr: BinaryExpression, pleftVal: NumericLiteralValue?, prightVal: NumericLiteralValue?): Expression {
-        if(pleftVal==null && prightVal==null)
-            return pexpr
-
-        val (expr, _, rightVal) = reorderAssociative(pexpr, pleftVal)
-        if(rightVal!=null) {
-            // right value is a constant, see if we can optimize
-            val leftValue: Expression = expr.left
-            val rightConst: NumericLiteralValue = rightVal
-            when(val cv = rightConst.number.toDouble()) {
-                -1.0 -> {
-                    // -left
-                    optimizationsDone++
-                    return PrefixExpression("-", leftValue, expr.position)
-                }
-                0.0 -> {
-                    // 0
-                    optimizationsDone++
-                    return NumericLiteralValue(rightConst.type, 0, expr.position)
-                }
-                1.0 -> {
-                    // left
-                    optimizationsDone++
-                    return expr.left
-                }
-                in powersOfTwo -> {
-                    if(leftValue.inferType(program).typeOrElse(DataType.STRUCT) in IntegerDatatypes) {
-                        // times a power of two => shift left
-                        optimizationsDone++
-                        val numshifts = log2(cv).toInt()
-                        return BinaryExpression(expr.left, "<<", NumericLiteralValue.optimalInteger(numshifts, expr.position), expr.position)
-                    }
-                }
-                in negativePowersOfTwo -> {
-                    if(leftValue.inferType(program).typeOrElse(DataType.STRUCT) in IntegerDatatypes) {
-                        // times a negative power of two => negate, then shift left
-                        optimizationsDone++
-                        val numshifts = log2(-cv).toInt()
-                        return BinaryExpression(PrefixExpression("-", expr.left, expr.position), "<<", NumericLiteralValue.optimalInteger(numshifts, expr.position), expr.position)
-                    }
-                }
-            }
-        }
-        // no need to check for left val constant (because of associativity)
-
-        return expr
-    }
-
-    private fun optimizeShiftLeft(expr: BinaryExpression, amountLv: NumericLiteralValue?): Expression {
-        if(amountLv==null)
-            return expr
-
-        val amount=amountLv.number.toInt()
-        if(amount==0) {
-            optimizationsDone++
-            return expr.left
-        }
-        val targetDt = expr.left.inferType(program).typeOrElse(DataType.STRUCT)
-        when(targetDt) {
-            DataType.UBYTE, DataType.BYTE -> {
-                if(amount>=8) {
-                    optimizationsDone++
-                    return NumericLiteralValue.optimalInteger(0, expr.position)
-                }
-            }
-            DataType.UWORD, DataType.WORD -> {
-                if(amount>=16) {
-                    optimizationsDone++
-                    return NumericLiteralValue.optimalInteger(0, expr.position)
-                }
-                else if(amount>=8) {
-                    optimizationsDone++
-                    val lsb=TypecastExpression(expr.left, DataType.UBYTE, true, expr.position)
-                    if(amount==8) {
-                        return FunctionCall(IdentifierReference(listOf("mkword"), expr.position), mutableListOf(NumericLiteralValue.optimalInteger(0, expr.position), lsb), expr.position)
-                    }
-                    val shifted = BinaryExpression(lsb, "<<", NumericLiteralValue.optimalInteger(amount-8, expr.position), expr.position)
-                    return FunctionCall(IdentifierReference(listOf("mkword"), expr.position), mutableListOf(NumericLiteralValue.optimalInteger(0, expr.position), shifted), expr.position)
-                }
-            }
-            else -> {}
-        }
-        return expr
-    }
-
-    private fun optimizeShiftRight(expr: BinaryExpression, amountLv: NumericLiteralValue?): Expression {
-        if(amountLv==null)
-            return expr
-
-        val amount=amountLv.number.toInt()
-        if(amount==0) {
-            optimizationsDone++
-            return expr.left
-        }
-        val targetDt = expr.left.inferType(program).typeOrElse(DataType.STRUCT)
-        when(targetDt) {
-            DataType.UBYTE -> {
-                if(amount>=8) {
-                    optimizationsDone++
-                    return NumericLiteralValue.optimalInteger(0, expr.position)
-                }
-            }
-            DataType.BYTE -> {
-                if(amount>8) {
-                    expr.right = NumericLiteralValue.optimalInteger(8, expr.right.position)
-                    return expr
-                }
-            }
-            DataType.UWORD -> {
-                if(amount>=16) {
-                    optimizationsDone++
-                    return NumericLiteralValue.optimalInteger(0, expr.position)
-                }
-                else if(amount>=8) {
-                    optimizationsDone++
-                    val msb=FunctionCall(IdentifierReference(listOf("msb"), expr.position), mutableListOf(expr.left), expr.position)
-                    if(amount==8)
-                        return msb
-                    return BinaryExpression(msb, ">>", NumericLiteralValue.optimalInteger(amount-8, expr.position), expr.position)
-                }
-            }
-            DataType.WORD -> {
-                if(amount>16) {
-                    expr.right = NumericLiteralValue.optimalInteger(16, expr.right.position)
-                    return expr
-                } else if(amount>=8) {
-                    optimizationsDone++
-                    val msbAsByte = TypecastExpression(
-                            FunctionCall(IdentifierReference(listOf("msb"), expr.position), mutableListOf(expr.left), expr.position),
-                            DataType.BYTE,
-                            true, expr.position)
-                    if(amount==8)
-                        return msbAsByte
-                    return BinaryExpression(msbAsByte, ">>", NumericLiteralValue.optimalInteger(amount-8, expr.position), expr.position)
-                }
-            }
-            else -> {}
-        }
-        return expr
-    }
-}
@@ -1,12 +1,12 @@
 package prog8.optimizer

 import prog8.ast.INameScope
-import prog8.ast.Module
 import prog8.ast.Node
 import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.expressions.*
-import prog8.ast.processing.IAstModifyingVisitor
+import prog8.ast.processing.AstWalker
+import prog8.ast.processing.IAstModification
 import prog8.ast.processing.IAstVisitor
 import prog8.ast.statements.*
 import prog8.compiler.target.CompilationTarget
@@ -14,95 +14,38 @@ import prog8.functions.BuiltinFunctions
 import kotlin.math.floor


-/*
-    TODO: remove unreachable code after return and exit()
-    TODO: proper inlining of tiny subroutines (at first, restrict to subs without parameters and variables in them, and build it up from there: correctly renaming/relocating all variables in them and refs to those as well)
-*/
-
-
 internal class StatementOptimizer(private val program: Program,
-                                  private val errors: ErrorReporter) : IAstModifyingVisitor {
-    var optimizationsDone: Int = 0
-        private set
+                                  private val errors: ErrorReporter) : AstWalker() {

-    private val pureBuiltinFunctions = BuiltinFunctions.filter { it.value.pure }
+    private val noModifications = emptyList<IAstModification>()
    private val callgraph = CallGraph(program)
-    private val vardeclsToRemove = mutableListOf<VarDecl>()
+    private val pureBuiltinFunctions = BuiltinFunctions.filter { it.value.pure }

-    override fun visit(program: Program) {
-        removeUnusedCode(callgraph)
-        super.visit(program)
-
-        for(decl in vardeclsToRemove) {
-            decl.definingScope().remove(decl)
-        }
-    }
-
-    private fun removeUnusedCode(callgraph: CallGraph) {
-        // remove all subroutines that aren't called, or are empty
-        val removeSubroutines = mutableSetOf<Subroutine>()
-        val entrypoint = program.entrypoint()
-        program.modules.forEach {
-            callgraph.forAllSubroutines(it) { sub ->
-                if (sub !== entrypoint && !sub.keepAlways && (sub.calledBy.isEmpty() || (sub.containsNoCodeNorVars() && !sub.isAsmSubroutine)))
-                    removeSubroutines.add(sub)
-            }
-        }
-
-        if (removeSubroutines.isNotEmpty()) {
-            removeSubroutines.forEach {
-                it.definingScope().remove(it)
-            }
-        }
-
-        val removeBlocks = mutableSetOf<Block>()
-        program.modules.flatMap { it.statements }.filterIsInstance<Block>().forEach { block ->
-            if (block.containsNoCodeNorVars() && "force_output" !in block.options())
-                removeBlocks.add(block)
-        }
-
-        if (removeBlocks.isNotEmpty()) {
-            removeBlocks.forEach { it.definingScope().remove(it) }
-        }
-
-        // remove modules that are not imported, or are empty (unless it's a library modules)
-        val removeModules = mutableSetOf<Module>()
-        program.modules.forEach {
-            if (!it.isLibraryModule && (it.importedBy.isEmpty() || it.containsNoCodeNorVars()))
-                removeModules.add(it)
-        }
-
-        if (removeModules.isNotEmpty()) {
-            program.modules.removeAll(removeModules)
-        }
-    }
-
-    override fun visit(block: Block): Statement {
+    override fun after(block: Block, parent: Node): Iterable<IAstModification> {
        if("force_output" !in block.options()) {
            if (block.containsNoCodeNorVars()) {
-                optimizationsDone++
                errors.warn("removing empty block '${block.name}'", block.position)
-                return NopStatement.insteadOf(block)
+                return listOf(IAstModification.Remove(block, parent))
            }

            if (block !in callgraph.usedSymbols) {
-                optimizationsDone++
                errors.warn("removing unused block '${block.name}'", block.position)
-                return NopStatement.insteadOf(block)  // remove unused block
+                return listOf(IAstModification.Remove(block, parent))
            }
        }
-
-        return super.visit(block)
+        return noModifications
    }

-    override fun visit(subroutine: Subroutine): Statement {
-        super.visit(subroutine)
+    override fun after(subroutine: Subroutine, parent: Node): Iterable<IAstModification> {
        val forceOutput = "force_output" in subroutine.definingBlock().options()
        if(subroutine.asmAddress==null && !forceOutput) {
            if(subroutine.containsNoCodeNorVars()) {
                errors.warn("removing empty subroutine '${subroutine.name}'", subroutine.position)
-                optimizationsDone++
-                return NopStatement.insteadOf(subroutine)
+                val removals = callgraph.calledBy.getValue(subroutine).map {
+                    IAstModification.Remove(it, it.parent)
+                }.toMutableList()
+                removals += IAstModification.Remove(subroutine, parent)
+                return removals
            }
        }

@@ -113,24 +56,398 @@ internal class StatementOptimizer(private val program: Program,

        if(subroutine !in callgraph.usedSymbols && !forceOutput) {
            errors.warn("removing unused subroutine '${subroutine.name}'", subroutine.position)
-            optimizationsDone++
-            return NopStatement.insteadOf(subroutine)
+            return listOf(IAstModification.Remove(subroutine, parent))
        }

-        visitStatements(subroutine.statements)
-        return subroutine
+        return noModifications
    }

-    override fun visit(decl: VarDecl): Statement {
+    override fun after(scope: AnonymousScope, parent: Node): Iterable<IAstModification> {
+        val linesToRemove = deduplicateAssignments(scope.statements)
+        return linesToRemove.reversed().map { IAstModification.Remove(scope.statements[it], scope) }
+    }
+
+    override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
        val forceOutput = "force_output" in decl.definingBlock().options()
        if(decl !in callgraph.usedSymbols && !forceOutput) {
            if(decl.type == VarDeclType.VAR)
-                errors.warn("removing unused variable ${decl.type} '${decl.name}'", decl.position)
-            optimizationsDone++
-            return NopStatement.insteadOf(decl)
+                errors.warn("removing unused variable '${decl.name}'", decl.position)
+
+            return listOf(IAstModification.Remove(decl, parent))
        }

-        return super.visit(decl)
+        return noModifications
+    }
+
+    override fun after(functionCallStatement: FunctionCallStatement, parent: Node): Iterable<IAstModification> {
+        if(functionCallStatement.target.nameInSource.size==1 && functionCallStatement.target.nameInSource[0] in BuiltinFunctions) {
+            val functionName = functionCallStatement.target.nameInSource[0]
+            if (functionName in pureBuiltinFunctions) {
+                errors.warn("statement has no effect (function return value is discarded)", functionCallStatement.position)
+                return listOf(IAstModification.Remove(functionCallStatement, parent))
+            }
+        }
+
+        // printing a literal string of just 2 or 1 characters is replaced by directly outputting those characters
+        // this is a C-64 specific optimization
+        if(functionCallStatement.target.nameInSource==listOf("c64scr", "print")) {
+            val arg = functionCallStatement.args.single()
+            val stringVar: IdentifierReference?
+            stringVar = if(arg is AddressOf) {
+                arg.identifier
+            } else {
+                arg as? IdentifierReference
+            }
+            if(stringVar!=null) {
+                val vardecl = stringVar.targetVarDecl(program.namespace)!!
+                val string = vardecl.value as? StringLiteralValue
+                if(string!=null) {
+                    val pos = functionCallStatement.position
+                    if (string.value.length == 1) {
+                        val firstCharEncoded = CompilationTarget.instance.encodeString(string.value, string.altEncoding)[0]
+                        val chrout = FunctionCallStatement(
+                                IdentifierReference(listOf("c64", "CHROUT"), pos),
+                                mutableListOf(NumericLiteralValue(DataType.UBYTE, firstCharEncoded.toInt(), pos)),
+                                functionCallStatement.void, pos
+                        )
+                        return listOf(IAstModification.ReplaceNode(functionCallStatement, chrout, parent))
+                    } else if (string.value.length == 2) {
+                        val firstTwoCharsEncoded = CompilationTarget.instance.encodeString(string.value.take(2), string.altEncoding)
+                        val chrout1 = FunctionCallStatement(
+                                IdentifierReference(listOf("c64", "CHROUT"), pos),
+                                mutableListOf(NumericLiteralValue(DataType.UBYTE, firstTwoCharsEncoded[0].toInt(), pos)),
+                                functionCallStatement.void, pos
+                        )
+                        val chrout2 = FunctionCallStatement(
+                                IdentifierReference(listOf("c64", "CHROUT"), pos),
+                                mutableListOf(NumericLiteralValue(DataType.UBYTE, firstTwoCharsEncoded[1].toInt(), pos)),
+                                functionCallStatement.void, pos
+                        )
+                        val anonscope = AnonymousScope(mutableListOf(), pos)
+                        anonscope.statements.add(chrout1)
+                        anonscope.statements.add(chrout2)
+                        return listOf(IAstModification.ReplaceNode(functionCallStatement, anonscope, parent))
+                    }
+                }
+            }
+        }
+
+        // if the first instruction in the called subroutine is a return statement, remove the jump altogeter
+        val subroutine = functionCallStatement.target.targetSubroutine(program.namespace)
+        if(subroutine!=null) {
+            val first = subroutine.statements.asSequence().filterNot { it is VarDecl || it is Directive }.firstOrNull()
+            if(first is Return)
+                return listOf(IAstModification.Remove(functionCallStatement, parent))
+        }
+
+        return noModifications
+    }
+
+    override fun before(functionCall: FunctionCall, parent: Node): Iterable<IAstModification> {
+        // if the first instruction in the called subroutine is a return statement with constant value, replace with the constant value
+        val subroutine = functionCall.target.targetSubroutine(program.namespace)
+        if(subroutine!=null) {
+            val first = subroutine.statements.asSequence().filterNot { it is VarDecl || it is Directive }.firstOrNull()
+            if(first is Return && first.value!=null) {
+                val constval = first.value?.constValue(program)
+                if(constval!=null)
+                    return listOf(IAstModification.ReplaceNode(functionCall, constval, parent))
+            }
+        }
+        return noModifications
+    }
+
+    override fun after(ifStatement: IfStatement, parent: Node): Iterable<IAstModification> {
+        // remove empty if statements
+        if(ifStatement.truepart.containsNoCodeNorVars() && ifStatement.elsepart.containsNoCodeNorVars())
+            return listOf(IAstModification.Remove(ifStatement, parent))
+
+        // empty true part? switch with the else part
+        if(ifStatement.truepart.containsNoCodeNorVars() && ifStatement.elsepart.containsCodeOrVars()) {
+            val invertedCondition = PrefixExpression("not", ifStatement.condition, ifStatement.condition.position)
+            val emptyscope = AnonymousScope(mutableListOf(), ifStatement.elsepart.position)
+            val truepart = AnonymousScope(ifStatement.elsepart.statements, ifStatement.truepart.position)
+            return listOf(
+                    IAstModification.ReplaceNode(ifStatement.condition, invertedCondition, ifStatement),
+                    IAstModification.ReplaceNode(ifStatement.truepart, truepart, ifStatement),
+                    IAstModification.ReplaceNode(ifStatement.elsepart, emptyscope, ifStatement)
+            )
+        }
+
+        val constvalue = ifStatement.condition.constValue(program)
+        if(constvalue!=null) {
+            return if(constvalue.asBooleanValue){
+                // always true -> keep only if-part
+                errors.warn("condition is always true", ifStatement.position)
+                listOf(IAstModification.ReplaceNode(ifStatement, ifStatement.truepart, parent))
+            } else {
+                // always false -> keep only else-part
+                errors.warn("condition is always false", ifStatement.position)
+                listOf(IAstModification.ReplaceNode(ifStatement, ifStatement.elsepart, parent))
+            }
+        }
+
+        return noModifications
+    }
+
+    override fun after(forLoop: ForLoop, parent: Node): Iterable<IAstModification> {
+        if(forLoop.body.containsNoCodeNorVars()) {
+            errors.warn("removing empty for loop", forLoop.position)
+            return listOf(IAstModification.Remove(forLoop, parent))
+        } else if(forLoop.body.statements.size==1) {
+            val loopvar = forLoop.body.statements[0] as? VarDecl
+            if(loopvar!=null && loopvar.name==forLoop.loopVar.nameInSource.singleOrNull()) {
+                // remove empty for loop (only loopvar decl in it)
+                return listOf(IAstModification.Remove(forLoop, parent))
+            }
+        }
+
+        val range = forLoop.iterable as? RangeExpr
+        if(range!=null) {
+            if(range.size()==1) {
+                // for loop over a (constant) range of just a single value-- optimize the loop away
+                // loopvar/reg = range value , follow by block
+                val scope = AnonymousScope(mutableListOf(), forLoop.position)
+                scope.statements.add(Assignment(AssignTarget(forLoop.loopVar, null, null, forLoop.position), range.from, forLoop.position))
+                scope.statements.addAll(forLoop.body.statements)
+                return listOf(IAstModification.ReplaceNode(forLoop, scope, parent))
+            }
+        }
+        val iterable = (forLoop.iterable as? IdentifierReference)?.targetVarDecl(program.namespace)
+        if(iterable!=null) {
+            if(iterable.datatype==DataType.STR) {
+                val sv = iterable.value as StringLiteralValue
+                val size = sv.value.length
+                if(size==1) {
+                    // loop over string of length 1 -> just assign the single character
+                    val character = CompilationTarget.instance.encodeString(sv.value, sv.altEncoding)[0]
+                    val byte = NumericLiteralValue(DataType.UBYTE, character, iterable.position)
+                    val scope = AnonymousScope(mutableListOf(), forLoop.position)
+                    scope.statements.add(Assignment(AssignTarget(forLoop.loopVar, null, null, forLoop.position), byte, forLoop.position))
+                    scope.statements.addAll(forLoop.body.statements)
+                    return listOf(IAstModification.ReplaceNode(forLoop, scope, parent))
+                }
+            }
+            else if(iterable.datatype in ArrayDatatypes) {
+                val size = iterable.arraysize!!.constIndex()
+                if(size==1) {
+                    // loop over array of length 1 -> just assign the single value
+                    val av = (iterable.value as ArrayLiteralValue).value[0].constValue(program)?.number
+                    if(av!=null) {
+                        val scope = AnonymousScope(mutableListOf(), forLoop.position)
+                        scope.statements.add(Assignment(
+                                AssignTarget(forLoop.loopVar, null, null, forLoop.position), NumericLiteralValue.optimalInteger(av.toInt(), iterable.position),
+                                forLoop.position))
+                        scope.statements.addAll(forLoop.body.statements)
+                        return listOf(IAstModification.ReplaceNode(forLoop, scope, parent))
+                    }
+                }
+            }
+        }
+
+        return noModifications
+    }
+
+    override fun before(untilLoop: UntilLoop, parent: Node): Iterable<IAstModification> {
+        val constvalue = untilLoop.untilCondition.constValue(program)
+        if(constvalue!=null) {
+            if(constvalue.asBooleanValue) {
+                // always true -> keep only the statement block (if there are no break statements)
+                errors.warn("condition is always true", untilLoop.untilCondition.position)
+                if(!hasBreak(untilLoop.body))
+                    return listOf(IAstModification.ReplaceNode(untilLoop, untilLoop.body, parent))
+            } else {
+                // always false
+                val forever = RepeatLoop(null, untilLoop.body, untilLoop.position)
+                return listOf(IAstModification.ReplaceNode(untilLoop, forever, parent))
+            }
+        }
+        return noModifications
+    }
+
+    override fun before(whileLoop: WhileLoop, parent: Node): Iterable<IAstModification> {
+        val constvalue = whileLoop.condition.constValue(program)
+        if(constvalue!=null) {
+            return if(constvalue.asBooleanValue) {
+                // always true
+                val forever = RepeatLoop(null, whileLoop.body, whileLoop.position)
+                listOf(IAstModification.ReplaceNode(whileLoop, forever, parent))
+            } else {
+                // always false -> remove the while statement altogether
+                errors.warn("condition is always false", whileLoop.condition.position)
+                listOf(IAstModification.Remove(whileLoop, parent))
+            }
+        }
+        return noModifications
+    }
+
+    override fun after(repeatLoop: RepeatLoop, parent: Node): Iterable<IAstModification> {
+        val iter = repeatLoop.iterations
+        if(iter!=null) {
+            if(repeatLoop.body.containsNoCodeNorVars()) {
+                errors.warn("empty loop removed", repeatLoop.position)
+                return listOf(IAstModification.Remove(repeatLoop, parent))
+            }
+            val iterations = iter.constValue(program)?.number?.toInt()
+            if (iterations == 0) {
+                errors.warn("iterations is always 0, removed loop", iter.position)
+                return listOf(IAstModification.Remove(repeatLoop, parent))
+            }
+            if (iterations == 1) {
+                errors.warn("iterations is always 1", iter.position)
+                return listOf(IAstModification.ReplaceNode(repeatLoop, repeatLoop.body, parent))
+            }
+        }
+        return noModifications
+    }
+
+    override fun after(whenStatement: WhenStatement, parent: Node): Iterable<IAstModification> {
+        // remove empty choices
+        class ChoiceRemover(val choice: WhenChoice) : IAstModification {
+            override fun perform() {
+                whenStatement.choices.remove(choice)
+            }
+        }
+        return whenStatement.choices
+                .filter { !it.statements.containsCodeOrVars() }
+                .map { ChoiceRemover(it) }
+    }
+
+    override fun after(jump: Jump, parent: Node): Iterable<IAstModification> {
+        // if the jump is to the next statement, remove the jump
+        val scope = jump.definingScope()
+        val label = jump.identifier?.targetStatement(scope)
+        if(label!=null && scope.statements.indexOf(label) == scope.statements.indexOf(jump)+1)
+            return listOf(IAstModification.Remove(jump, parent))
+
+        return noModifications
+    }
+
+    override fun before(assignment: Assignment, parent: Node): Iterable<IAstModification> {
+
+        val binExpr = assignment.value as? BinaryExpression
+        if(binExpr!=null) {
+            if(binExpr.left isSameAs assignment.target) {
+                val rExpr = binExpr.right as? BinaryExpression
+                if(rExpr!=null) {
+                    val op1 = binExpr.operator
+                    val op2 = rExpr.operator
+
+                    if(rExpr.left is NumericLiteralValue && op2 in setOf("+", "*", "&", "|")) {
+                        // associative operator, make sure the constant numeric value is second (right)
+                        return listOf(IAstModification.SwapOperands(rExpr))
+                    }
+
+                    val rNum = (rExpr.right as? NumericLiteralValue)?.number
+                    if(rNum!=null) {
+                        if (op1 == "+" || op1 == "-") {
+                            if (op2 == "+") {
+                                // A = A +/- B + N
+                                val expr2 = BinaryExpression(binExpr.left, binExpr.operator, rExpr.left, binExpr.position)
+                                val addConstant = Assignment(
+                                        assignment.target,
+                                        BinaryExpression(binExpr.left, "+", rExpr.right, rExpr.position),
+                                        assignment.position
+                                )
+                                return listOf(
+                                        IAstModification.ReplaceNode(binExpr, expr2, binExpr.parent),
+                                        IAstModification.InsertAfter(assignment, addConstant, parent))
+                            } else if (op2 == "-") {
+                                // A = A +/- B - N
+                                val expr2 = BinaryExpression(binExpr.left, binExpr.operator, rExpr.left, binExpr.position)
+                                val subConstant = Assignment(
+                                        assignment.target,
+                                        BinaryExpression(binExpr.left, "-", rExpr.right, rExpr.position),
+                                        assignment.position
+                                )
+                                return listOf(
+                                        IAstModification.ReplaceNode(binExpr, expr2, binExpr.parent),
+                                        IAstModification.InsertAfter(assignment, subConstant, parent))
+                            }
+                        }
+                    }
+                }
+            }
+
+            if(binExpr.operator in associativeOperators && binExpr.right isSameAs assignment.target) {
+                // associative operator, swap the operands so that the assignment target is first (left)
+                // unless the other operand is the same in which case we don't swap (endless loop!)
+                if (!(binExpr.left isSameAs binExpr.right))
+                    return listOf(IAstModification.SwapOperands(binExpr))
+            }
+
+        }
+
+        return noModifications
+    }
+
+    override fun after(assignment: Assignment, parent: Node): Iterable<IAstModification> {
+        if(assignment.target isSameAs assignment.value) {
+            // remove assignment to self
+            return listOf(IAstModification.Remove(assignment, parent))
+        }
+
+        val targetIDt = assignment.target.inferType(program, assignment)
+        if(!targetIDt.isKnown)
+            throw FatalAstException("can't infer type of assignment target")
+
+        // optimize binary expressions a bit
+        val targetDt = targetIDt.typeOrElse(DataType.STRUCT)
+        val bexpr=assignment.value as? BinaryExpression
+        if(bexpr!=null) {
+            val cv = bexpr.right.constValue(program)?.number?.toDouble()
+            if (cv != null && assignment.target isSameAs bexpr.left) {
+                // assignments of the form:  X = X <operator> <expr>
+                // remove assignments that have no effect (such as X=X+0)
+                // optimize/rewrite some other expressions
+                val vardeclDt = (assignment.target.identifier?.targetVarDecl(program.namespace))?.type
+                when (bexpr.operator) {
+                    "+" -> {
+                        if (cv == 0.0) {
+                            return listOf(IAstModification.Remove(assignment, parent))
+                        } else if (targetDt in IntegerDatatypes && floor(cv) == cv) {
+                            if (vardeclDt != VarDeclType.MEMORY && cv in 1.0..4.0) {
+                                // replace by several INCs if it's not a memory address (inc on a memory mapped register doesn't work very well)
+                                val incs = AnonymousScope(mutableListOf(), assignment.position)
+                                repeat(cv.toInt()) {
+                                    incs.statements.add(PostIncrDecr(assignment.target, "++", assignment.position))
+                                }
+                                return listOf(IAstModification.ReplaceNode(assignment, incs, parent))
+                            }
+                        }
+                    }
+                    "-" -> {
+                        if (cv == 0.0) {
+                            return listOf(IAstModification.Remove(assignment, parent))
+                        } else if (targetDt in IntegerDatatypes && floor(cv) == cv) {
+                            if (vardeclDt != VarDeclType.MEMORY && cv in 1.0..4.0) {
+                                // replace by several DECs if it's not a memory address (dec on a memory mapped register doesn't work very well)
+                                val decs = AnonymousScope(mutableListOf(), assignment.position)
+                                repeat(cv.toInt()) {
+                                    decs.statements.add(PostIncrDecr(assignment.target, "--", assignment.position))
+                                }
+                                return listOf(IAstModification.ReplaceNode(assignment, decs, parent))
+                            }
+                        }
+                    }
+                    "*" -> if (cv == 1.0) return listOf(IAstModification.Remove(assignment, parent))
+                    "/" -> if (cv == 1.0) return listOf(IAstModification.Remove(assignment, parent))
+                    "**" -> if (cv == 1.0) return listOf(IAstModification.Remove(assignment, parent))
+                    "|" -> if (cv == 0.0) return listOf(IAstModification.Remove(assignment, parent))
+                    "^" -> if (cv == 0.0) return listOf(IAstModification.Remove(assignment, parent))
+                    "<<" -> {
+                        if (cv == 0.0)
+                            return listOf(IAstModification.Remove(assignment, parent))
+                    }
+                    ">>" -> {
+                        if (cv == 0.0)
+                            return listOf(IAstModification.Remove(assignment, parent))
+                    }
+                }
+
+            }
+        }
+        return noModifications
    }

    private fun deduplicateAssignments(statements: List<Statement>): MutableList<Int> {
@@ -158,223 +475,17 @@ internal class StatementOptimizer(private val program: Program,
        return linesToRemove
    }

-    override fun visit(functionCallStatement: FunctionCallStatement): Statement {
-        if(functionCallStatement.target.nameInSource.size==1 && functionCallStatement.target.nameInSource[0] in BuiltinFunctions) {
-            val functionName = functionCallStatement.target.nameInSource[0]
-            if (functionName in pureBuiltinFunctions) {
-                errors.warn("statement has no effect (function return value is discarded)", functionCallStatement.position)
-                optimizationsDone++
-                return NopStatement.insteadOf(functionCallStatement)
-            }
-        }
+    private fun hasBreak(scope: INameScope): Boolean {

-        if(functionCallStatement.target.nameInSource==listOf("c64scr", "print") ||
-                functionCallStatement.target.nameInSource==listOf("c64scr", "print_p")) {
-            // printing a literal string of just 2 or 1 characters is replaced by directly outputting those characters
-            val arg = functionCallStatement.args.single()
-            val stringVar: IdentifierReference?
-            stringVar = if(arg is AddressOf) {
-                arg.identifier
-            } else {
-                arg as? IdentifierReference
-            }
-            if(stringVar!=null) {
-                val vardecl = stringVar.targetVarDecl(program.namespace)!!
-                val string = vardecl.value!! as StringLiteralValue
-                if(string.value.length==1) {
-                    val firstCharEncoded = CompilationTarget.encodeString(string.value, string.altEncoding)[0]
-                    functionCallStatement.args.clear()
-                    functionCallStatement.args.add(NumericLiteralValue.optimalInteger(firstCharEncoded.toInt(), functionCallStatement.position))
-                    functionCallStatement.target = IdentifierReference(listOf("c64", "CHROUT"), functionCallStatement.target.position)
-                    vardeclsToRemove.add(vardecl)
-                    optimizationsDone++
-                    return functionCallStatement
-                } else if(string.value.length==2) {
-                    val firstTwoCharsEncoded = CompilationTarget.encodeString(string.value.take(2), string.altEncoding)
-                    val scope = AnonymousScope(mutableListOf(), functionCallStatement.position)
-                    scope.statements.add(FunctionCallStatement(IdentifierReference(listOf("c64", "CHROUT"), functionCallStatement.target.position),
-                            mutableListOf(NumericLiteralValue.optimalInteger(firstTwoCharsEncoded[0].toInt(), functionCallStatement.position)),
-                            functionCallStatement.void, functionCallStatement.position))
-                    scope.statements.add(FunctionCallStatement(IdentifierReference(listOf("c64", "CHROUT"), functionCallStatement.target.position),
-                            mutableListOf(NumericLiteralValue.optimalInteger(firstTwoCharsEncoded[1].toInt(), functionCallStatement.position)),
-                            functionCallStatement.void, functionCallStatement.position))
-                    vardeclsToRemove.add(vardecl)
-                    optimizationsDone++
-                    return scope
-                }
-            }
-        }
-
-        // if it calls a subroutine,
-        // and the first instruction in the subroutine is a jump, call that jump target instead
-        // if the first instruction in the subroutine is a return statement, replace with a nop instruction
-        val subroutine = functionCallStatement.target.targetSubroutine(program.namespace)
-        if(subroutine!=null) {
-            val first = subroutine.statements.asSequence().filterNot { it is VarDecl || it is Directive }.firstOrNull()
-            if(first is Jump && first.identifier!=null) {
-                optimizationsDone++
-                return FunctionCallStatement(first.identifier, functionCallStatement.args, functionCallStatement.void, functionCallStatement.position)
-            }
-            if(first is ReturnFromIrq || first is Return) {
-                optimizationsDone++
-                return NopStatement.insteadOf(functionCallStatement)
-            }
-        }
-
-        return super.visit(functionCallStatement)
-    }
-
-    override fun visit(functionCall: FunctionCall): Expression {
-        // if it calls a subroutine,
-        // and the first instruction in the subroutine is a jump, call that jump target instead
-        // if the first instruction in the subroutine is a return statement with constant value, replace with the constant value
-        val subroutine = functionCall.target.targetSubroutine(program.namespace)
-        if(subroutine!=null) {
-            val first = subroutine.statements.asSequence().filterNot { it is VarDecl || it is Directive }.firstOrNull()
-            if(first is Jump && first.identifier!=null) {
-                optimizationsDone++
-                return FunctionCall(first.identifier, functionCall.args, functionCall.position)
-            }
-            if(first is Return && first.value!=null) {
-                val constval = first.value?.constValue(program)
-                if(constval!=null)
-                    return constval
-            }
-        }
-        return super.visit(functionCall)
-    }
-
-    override fun visit(ifStatement: IfStatement): Statement {
-        super.visit(ifStatement)
-
-        if(ifStatement.truepart.containsNoCodeNorVars() && ifStatement.elsepart.containsNoCodeNorVars()) {
-            optimizationsDone++
-            return NopStatement.insteadOf(ifStatement)
-        }
-
-        if(ifStatement.truepart.containsNoCodeNorVars() && ifStatement.elsepart.containsCodeOrVars()) {
-            // invert the condition and move else part to true part
-            ifStatement.truepart = ifStatement.elsepart
-            ifStatement.elsepart = AnonymousScope(mutableListOf(), ifStatement.elsepart.position)
-            ifStatement.condition = PrefixExpression("not", ifStatement.condition, ifStatement.condition.position)
-            optimizationsDone++
-            return ifStatement
-        }
-
-        val constvalue = ifStatement.condition.constValue(program)
-        if(constvalue!=null) {
-            return if(constvalue.asBooleanValue){
-                // always true -> keep only if-part
-                errors.warn("condition is always true", ifStatement.position)
-                optimizationsDone++
-                ifStatement.truepart
-            } else {
-                // always false -> keep only else-part
-                errors.warn("condition is always false", ifStatement.position)
-                optimizationsDone++
-                ifStatement.elsepart
-            }
-        }
-        return ifStatement
-    }
-
-    override fun visit(forLoop: ForLoop): Statement {
-        super.visit(forLoop)
-        if(forLoop.body.containsNoCodeNorVars()) {
-            // remove empty for loop
-            optimizationsDone++
-            return NopStatement.insteadOf(forLoop)
-        } else if(forLoop.body.statements.size==1) {
-            val loopvar = forLoop.body.statements[0] as? VarDecl
-            if(loopvar!=null && loopvar.name==forLoop.loopVar?.nameInSource?.singleOrNull()) {
-                // remove empty for loop
-                optimizationsDone++
-                return NopStatement.insteadOf(forLoop)
-            }
-        }
-
-
-        val range = forLoop.iterable as? RangeExpr
-        if(range!=null) {
-            if(range.size()==1) {
-                // for loop over a (constant) range of just a single value-- optimize the loop away
-                // loopvar/reg = range value , follow by block
-                val assignment = Assignment(AssignTarget(forLoop.loopRegister, forLoop.loopVar, null, null, forLoop.position), null, range.from, forLoop.position)
-                forLoop.body.statements.add(0, assignment)
-                optimizationsDone++
-                return forLoop.body
-            }
-        }
-        return forLoop
-    }
-
-    override fun visit(whileLoop: WhileLoop): Statement {
-        super.visit(whileLoop)
-        val constvalue = whileLoop.condition.constValue(program)
-        if(constvalue!=null) {
-            return if(constvalue.asBooleanValue){
-                // always true -> print a warning, and optimize into a forever-loop
-                errors.warn("condition is always true", whileLoop.condition.position)
-                optimizationsDone++
-                ForeverLoop(whileLoop.body, whileLoop.position)
-            } else {
-                // always false -> remove the while statement altogether
-                errors.warn("condition is always false", whileLoop.condition.position)
-                optimizationsDone++
-                NopStatement.insteadOf(whileLoop)
-            }
-        }
-        return whileLoop
-    }
-
-    override fun visit(repeatLoop: RepeatLoop): Statement {
-        super.visit(repeatLoop)
-        val constvalue = repeatLoop.untilCondition.constValue(program)
-        if(constvalue!=null) {
-            return if(constvalue.asBooleanValue){
-                // always true -> keep only the statement block (if there are no continue and break statements)
-                errors.warn("condition is always true", repeatLoop.untilCondition.position)
-                if(hasContinueOrBreak(repeatLoop.body))
-                    repeatLoop
-                else {
-                    optimizationsDone++
-                    repeatLoop.body
-                }
-            } else {
-                // always false -> print a warning, and optimize into a forever loop
-                errors.warn("condition is always false", repeatLoop.untilCondition.position)
-                optimizationsDone++
-                ForeverLoop(repeatLoop.body, repeatLoop.position)
-            }
-        }
-        return repeatLoop
-    }
-
-    override fun visit(whenStatement: WhenStatement): Statement {
-        val choices = whenStatement.choices.toList()
-        for(choice in choices) {
-            if(choice.statements.containsNoCodeNorVars())
-                whenStatement.choices.remove(choice)
-        }
-        return super.visit(whenStatement)
-    }
-
-    private fun hasContinueOrBreak(scope: INameScope): Boolean {
-
-        class Searcher: IAstModifyingVisitor
+        class Searcher: IAstVisitor
        {
            var count=0

-            override fun visit(breakStmt: Break): Statement {
+            override fun visit(breakStmt: Break) {
                count++
-                return super.visit(breakStmt)
-            }
-
-            override fun visit(contStmt: Continue): Statement {
-                count++
-                return super.visit(contStmt)
            }
        }
+
        val s=Searcher()
        for(stmt in scope.statements) {
            stmt.accept(s)
@@ -384,237 +495,4 @@ internal class StatementOptimizer(private val program: Program,
        return s.count > 0
    }

-    override fun visit(jump: Jump): Statement {
-        val subroutine = jump.identifier?.targetSubroutine(program.namespace)
-        if(subroutine!=null) {
-            // if the first instruction in the subroutine is another jump, shortcut this one
-            val first = subroutine.statements.asSequence().filterNot { it is VarDecl || it is Directive }.firstOrNull()
-            if(first is Jump) {
-                optimizationsDone++
-                return first
-            }
-        }
-
-        // if the jump is to the next statement, remove the jump
-        val scope = jump.definingScope()
-        val label = jump.identifier?.targetStatement(scope)
-        if(label!=null) {
-            if(scope.statements.indexOf(label) == scope.statements.indexOf(jump)+1) {
-                optimizationsDone++
-                return NopStatement.insteadOf(jump)
-            }
-        }
-
-        return jump
-    }
-
-    override fun visit(assignment: Assignment): Statement {
-        if(assignment.aug_op!=null)
-            throw AstException("augmented assignments should have been converted to normal assignments before this optimizer: $assignment")
-
-        if(assignment.target isSameAs assignment.value) {
-            if(assignment.target.isNotMemory(program.namespace)) {
-                optimizationsDone++
-                return NopStatement.insteadOf(assignment)
-            }
-        }
-        val targetIDt = assignment.target.inferType(program, assignment)
-        if(!targetIDt.isKnown)
-            throw FatalAstException("can't infer type of assignment target")
-        val targetDt = targetIDt.typeOrElse(DataType.STRUCT)
-        val bexpr=assignment.value as? BinaryExpression
-        if(bexpr!=null) {
-            val cv = bexpr.right.constValue(program)?.number?.toDouble()
-            if (cv == null) {
-                if (bexpr.operator == "+" && targetDt != DataType.FLOAT) {
-                    if (bexpr.left isSameAs bexpr.right && assignment.target isSameAs bexpr.left) {
-                        bexpr.operator = "*"
-                        bexpr.right = NumericLiteralValue.optimalInteger(2, assignment.value.position)
-                        optimizationsDone++
-                        return assignment
-                    }
-                }
-            } else {
-                if (assignment.target isSameAs bexpr.left) {
-                    // remove assignments that have no effect  X=X , X+=0, X-=0, X*=1, X/=1, X//=1, A |= 0, A ^= 0, A<<=0, etc etc
-                    // A = A <operator> B
-                    val vardeclDt = (assignment.target.identifier?.targetVarDecl(program.namespace))?.type
-
-                    when (bexpr.operator) {
-                        "+" -> {
-                            if (cv == 0.0) {
-                                optimizationsDone++
-                                return NopStatement.insteadOf(assignment)
-                            } else if (targetDt in IntegerDatatypes && floor(cv) == cv) {
-                                if ((vardeclDt == VarDeclType.MEMORY && cv in 1.0..3.0) || (vardeclDt != VarDeclType.MEMORY && cv in 1.0..8.0)) {
-                                    // replace by several INCs (a bit less when dealing with memory targets)
-                                    val decs = AnonymousScope(mutableListOf(), assignment.position)
-                                    repeat(cv.toInt()) {
-                                        decs.statements.add(PostIncrDecr(assignment.target, "++", assignment.position))
-                                    }
-                                    return decs
-                                }
-                            }
-                        }
-                        "-" -> {
-                            if (cv == 0.0) {
-                                optimizationsDone++
-                                return NopStatement.insteadOf(assignment)
-                            } else if (targetDt in IntegerDatatypes && floor(cv) == cv) {
-                                if ((vardeclDt == VarDeclType.MEMORY && cv in 1.0..3.0) || (vardeclDt != VarDeclType.MEMORY && cv in 1.0..8.0)) {
-                                    // replace by several DECs (a bit less when dealing with memory targets)
-                                    val decs = AnonymousScope(mutableListOf(), assignment.position)
-                                    repeat(cv.toInt()) {
-                                        decs.statements.add(PostIncrDecr(assignment.target, "--", assignment.position))
-                                    }
-                                    return decs
-                                }
-                            }
-                        }
-                        "*" -> if (cv == 1.0) {
-                            optimizationsDone++
-                            return NopStatement.insteadOf(assignment)
-                        }
-                        "/" -> if (cv == 1.0) {
-                            optimizationsDone++
-                            return NopStatement.insteadOf(assignment)
-                        }
-                        "**" -> if (cv == 1.0) {
-                            optimizationsDone++
-                            return NopStatement.insteadOf(assignment)
-                        }
-                        "|" -> if (cv == 0.0) {
-                            optimizationsDone++
-                            return NopStatement.insteadOf(assignment)
-                        }
-                        "^" -> if (cv == 0.0) {
-                            optimizationsDone++
-                            return NopStatement.insteadOf(assignment)
-                        }
-                        "<<" -> {
-                            if (cv == 0.0) {
-                                optimizationsDone++
-                                return NopStatement.insteadOf(assignment)
-                            }
-                            if (((targetDt == DataType.UWORD || targetDt == DataType.WORD) && cv > 15.0) ||
-                                    ((targetDt == DataType.UBYTE || targetDt == DataType.BYTE) && cv > 7.0)) {
-                                assignment.value = NumericLiteralValue.optimalInteger(0, assignment.value.position)
-                                assignment.value.linkParents(assignment)
-                                optimizationsDone++
-                            } else {
-                                // replace by in-place lsl(...) call
-                                val scope = AnonymousScope(mutableListOf(), assignment.position)
-                                var numshifts = cv.toInt()
-                                while (numshifts > 0) {
-                                    scope.statements.add(FunctionCallStatement(IdentifierReference(listOf("lsl"), assignment.position),
-                                            mutableListOf(bexpr.left), true, assignment.position))
-                                    numshifts--
-                                }
-                                optimizationsDone++
-                                return scope
-                            }
-                        }
-                        ">>" -> {
-                            if (cv == 0.0) {
-                                optimizationsDone++
-                                return NopStatement.insteadOf(assignment)
-                            }
-                            if ((targetDt == DataType.UWORD && cv > 15.0) || (targetDt == DataType.UBYTE && cv > 7.0)) {
-                                assignment.value = NumericLiteralValue.optimalInteger(0, assignment.value.position)
-                                assignment.value.linkParents(assignment)
-                                optimizationsDone++
-                            } else {
-                                // replace by in-place lsr(...) call
-                                val scope = AnonymousScope(mutableListOf(), assignment.position)
-                                var numshifts = cv.toInt()
-                                while (numshifts > 0) {
-                                    scope.statements.add(FunctionCallStatement(IdentifierReference(listOf("lsr"), assignment.position),
-                                            mutableListOf(bexpr.left), true, assignment.position))
-                                    numshifts--
-                                }
-                                optimizationsDone++
-                                return scope
-                            }
-                        }
-                    }
-                }
-            }
-        }
-
-
-        return super.visit(assignment)
-    }
-
-    override fun visit(scope: AnonymousScope): Statement {
-        val linesToRemove = deduplicateAssignments(scope.statements)
-        if(linesToRemove.isNotEmpty()) {
-            linesToRemove.reversed().forEach{scope.statements.removeAt(it)}
-        }
-        visitStatements(scope.statements)
-        return super.visit(scope)
-    }
-
-    override fun visit(label: Label): Statement {
-        // remove duplicate labels
-        val stmts = label.definingScope().statements
-        val startIdx = stmts.indexOf(label)
-        if(startIdx< stmts.lastIndex && stmts[startIdx+1] == label)
-            return NopStatement.insteadOf(label)
-
-        return super.visit(label)
-    }
-
-
-    private fun visitStatements(statements: MutableList<Statement>) {
-        // TODO remove all unreachable code statements after call to exit() or a return
-        // this is not yet correct because we still have nested subroutines
-//        val exitCallIndex = statements.indexOfFirst { it is FunctionCallStatement && it.target.nameInSource.last()=="exit" }
-//        if(exitCallIndex>=0) {
-//            while(exitCallIndex < statements.lastIndex) {
-//                val stmt  = statements[exitCallIndex+1]
-//                println("after exit() removing: $stmt")
-//                statements.removeAt(exitCallIndex+1)
-//            }
-//        }
-    }
-
-}
-
-
-
-internal class FlattenAnonymousScopesAndRemoveNops: IAstVisitor {
-    private var scopesToFlatten = mutableListOf<INameScope>()
-    private val nopStatements = mutableListOf<NopStatement>()
-
-    override fun visit(program: Program) {
-        super.visit(program)
-        for(scope in scopesToFlatten.reversed()) {
-            val namescope = scope.parent as INameScope
-            val idx = namescope.statements.indexOf(scope as Statement)
-            if(idx>=0) {
-                val nop = NopStatement.insteadOf(namescope.statements[idx])
-                nop.parent = namescope as Node
-                namescope.statements[idx] = nop
-                namescope.statements.addAll(idx, scope.statements)
-                scope.statements.forEach { it.parent = namescope }
-                visit(nop)
-            }
-        }
-
-        this.nopStatements.forEach {
-            it.definingScope().remove(it)
-        }
-    }
-
-    override fun visit(scope: AnonymousScope) {
-        if(scope.parent is INameScope) {
-            scopesToFlatten.add(scope)  // get rid of the anonymous scope
-        }
-
-        return super.visit(scope)
-    }
-
-    override fun visit(nopStatement: NopStatement) {
-        nopStatements.add(nopStatement)
-    }
 }
@@ -0,0 +1,69 @@
+package prog8.optimizer
+
+import prog8.ast.INameScope
+import prog8.ast.Node
+import prog8.ast.Program
+import prog8.ast.base.ErrorReporter
+import prog8.ast.processing.AstWalker
+import prog8.ast.processing.IAstModification
+import prog8.ast.statements.*
+
+internal class UnusedCodeRemover(private val errors: ErrorReporter): AstWalker() {
+
+    override fun before(program: Program, parent: Node): Iterable<IAstModification> {
+        val callgraph = CallGraph(program)
+        val removals = mutableListOf<IAstModification>()
+
+        // remove all subroutines that aren't called, or are empty
+        val entrypoint = program.entrypoint()
+        program.modules.forEach {
+            callgraph.forAllSubroutines(it) { sub ->
+                if (sub !== entrypoint && !sub.isAsmSubroutine && (callgraph.calledBy[sub].isNullOrEmpty() || sub.containsNoCodeNorVars())) {
+                    removals.add(IAstModification.Remove(sub, sub.definingScope() as Node))
+                }
+            }
+        }
+
+        program.modules.flatMap { it.statements }.filterIsInstance<Block>().forEach { block ->
+            if (block.containsNoCodeNorVars() && "force_output" !in block.options())
+                removals.add(IAstModification.Remove(block, block.definingScope() as Node))
+        }
+
+        // remove modules that are not imported, or are empty (unless it's a library modules)
+        program.modules.forEach {
+            if (!it.isLibraryModule && (it.importedBy.isEmpty() || it.containsNoCodeNorVars()))
+                removals.add(IAstModification.Remove(it, it.parent))
+        }
+
+        return removals
+    }
+
+
+    override fun before(breakStmt: Break, parent: Node): Iterable<IAstModification> {
+        reportUnreachable(breakStmt, parent as INameScope)
+        return emptyList()
+    }
+
+    override fun before(jump: Jump, parent: Node): Iterable<IAstModification> {
+        reportUnreachable(jump, parent as INameScope)
+        return emptyList()
+    }
+
+    override fun before(returnStmt: Return, parent: Node): Iterable<IAstModification> {
+        reportUnreachable(returnStmt, parent as INameScope)
+        return emptyList()
+    }
+
+    override fun before(functionCallStatement: FunctionCallStatement, parent: Node): Iterable<IAstModification> {
+        if(functionCallStatement.target.nameInSource.last() == "exit")
+            reportUnreachable(functionCallStatement, parent as INameScope)
+        return emptyList()
+    }
+
+    private fun reportUnreachable(stmt: Statement, parent: INameScope) {
+        when(val next = parent.nextSibling(stmt)) {
+            null, is Label, is Directive, is VarDecl, is InlineAssembly, is Subroutine, is StructDecl -> {}
+            else -> errors.warn("unreachable code", next.position)
+        }
+    }
+}
@@ -4,12 +4,12 @@ import org.antlr.v4.runtime.*
 import prog8.ast.Module
 import prog8.ast.Program
 import prog8.ast.antlr.toAst
-import prog8.ast.base.ErrorReporter
 import prog8.ast.base.Position
 import prog8.ast.base.SyntaxError
 import prog8.ast.base.checkImportedValid
 import prog8.ast.statements.Directive
 import prog8.ast.statements.DirectiveArg
+import prog8.compiler.target.CompilationTarget
 import prog8.pathFrom
 import java.io.InputStream
 import java.nio.file.Files
@@ -20,21 +20,13 @@ import java.nio.file.Paths
 internal class ParsingFailedError(override var message: String) : Exception(message)


-private class LexerErrorListener: BaseErrorListener() {
-    var  numberOfErrors: Int = 0
-    override fun syntaxError(p0: Recognizer<*, *>?, p1: Any?, p2: Int, p3: Int, p4: String?, p5: RecognitionException?) {
-        numberOfErrors++
-    }
-}
-
-
 internal class CustomLexer(val modulePath: Path, input: CharStream?) : prog8Lexer(input)


 internal fun moduleName(fileName: Path) = fileName.toString().substringBeforeLast('.')


-internal class ModuleImporter(private val errors: ErrorReporter) {
+internal class ModuleImporter {

    internal fun importModule(program: Program, filePath: Path): Module {
        print("importing '${moduleName(filePath.fileName)}'")
@@ -61,13 +53,28 @@ internal class ModuleImporter(private val errors: ErrorReporter) {
        return executeImportDirective(program, import, Paths.get(""))
    }

+    private class MyErrorListener: ConsoleErrorListener() {
+        var  numberOfErrors: Int = 0
+        override fun syntaxError(recognizer: Recognizer<*, *>?, offendingSymbol: Any?, line: Int, charPositionInLine: Int, msg: String, e: RecognitionException?) {
+            numberOfErrors++
+            when (recognizer) {
+                is CustomLexer -> System.err.println("${recognizer.modulePath}:$line:$charPositionInLine: $msg")
+                is prog8Parser -> System.err.println("${recognizer.inputStream.sourceName}:$line:$charPositionInLine: $msg")
+                else -> System.err.println("$line:$charPositionInLine $msg")
+            }
+        }
+    }
+
    private fun importModule(program: Program, stream: CharStream, modulePath: Path, isLibrary: Boolean): Module {
        val moduleName = moduleName(modulePath.fileName)
        val lexer = CustomLexer(modulePath, stream)
-        val lexerErrors = LexerErrorListener()
+        lexer.removeErrorListeners()
+        val lexerErrors = MyErrorListener()
        lexer.addErrorListener(lexerErrors)
        val tokens = CommentHandlingTokenStream(lexer)
        val parser = prog8Parser(tokens)
+        parser.removeErrorListeners()
+        parser.addErrorListener(MyErrorListener())
        val parseTree = parser.module()
        val numberOfErrors = parser.numberOfSyntaxErrors + lexerErrors.numberOfErrors
        if(numberOfErrors > 0)
@@ -95,7 +102,7 @@ internal class ModuleImporter(private val errors: ErrorReporter) {

    private fun discoverImportedModuleFile(name: String, source: Path, position: Position?): Path {
        val fileName = "$name.p8"
-        val locations = mutableListOf(source.parent)
+        val locations = if(source.toString().isEmpty()) mutableListOf<Path>() else mutableListOf(source.parent)

        val propPath = System.getProperty("prog8.libdir")
        if(propPath!=null)
@@ -110,7 +117,7 @@ internal class ModuleImporter(private val errors: ErrorReporter) {
            if (Files.isReadable(file)) return file
        }

-        throw ParsingFailedError("$position Import: no module source file '$fileName' found  (I've looked in: $locations)")
+        throw ParsingFailedError("$position Import: no module source file '$fileName' found  (I've looked in: embedded libs and $locations)")
    }

    private fun executeImportDirective(program: Program, import: Directive, source: Path): Module? {
@@ -129,10 +136,7 @@ internal class ModuleImporter(private val errors: ErrorReporter) {
                if(resource!=null) {
                    // load the module from the embedded resource
                    resource.use {
-                        if(import.args[0].int==42)
-                            println("importing '$moduleName' (library, auto)")
-                        else
-                            println("importing '$moduleName' (library)")
+                        println("importing '$moduleName' (library)")
                        importModule(program, CharStreams.fromStream(it), Paths.get("@embedded@/$moduleName"), true)
                    }
                } else {
@@ -140,11 +144,15 @@ internal class ModuleImporter(private val errors: ErrorReporter) {
                    importModule(program, modulePath)
                }

-        importedModule.checkImportedValid(errors)
+        importedModule.checkImportedValid()
        return importedModule
    }

    private fun tryGetEmbeddedResource(name: String): InputStream? {
+        val target = CompilationTarget.instance.name
+        val targetSpecific = object{}.javaClass.getResourceAsStream("/prog8lib/$target/$name")
+        if(targetSpecific!=null)
+            return targetSpecific
        return object{}.javaClass.getResourceAsStream("/prog8lib/$name")
    }
 }
@@ -1,658 +0,0 @@
-package prog8.vm
-
-import prog8.ast.base.ByteDatatypes
-import prog8.ast.base.DataType
-import prog8.ast.base.WordDatatypes
-import prog8.ast.expressions.ArrayLiteralValue
-import prog8.ast.expressions.NumericLiteralValue
-import prog8.ast.expressions.StringLiteralValue
-import prog8.vm.astvm.VmExecutionException
-import java.util.*
-import kotlin.math.abs
-import kotlin.math.pow
-
-
-/**
- * Rather than a literal value (NumericLiteralValue) that occurs in the parsed source code,
- * this runtime value can be used to *execute* the parsed Ast (or another intermediary form)
- * It contains a value of a variable during run time of the program and provides arithmetic operations on the value.
- */
-
-abstract class RuntimeValueBase(val type: DataType) {
-    abstract fun numericValue(): Number
-    abstract fun integerValue(): Int
-}
-
-
-class RuntimeValueNumeric(type: DataType, num: Number): RuntimeValueBase(type) {
-
-    val byteval: Short?
-    val wordval: Int?
-    val floatval: Double?
-    val asBoolean: Boolean
-
-    companion object {
-        fun fromLv(literalValue: NumericLiteralValue): RuntimeValueNumeric {
-            return RuntimeValueNumeric(literalValue.type, num = literalValue.number)
-        }
-    }
-
-    init {
-        when (type) {
-            DataType.UBYTE -> {
-                val inum = num.toInt()
-                require(inum in 0..255) { "invalid value for ubyte: $inum" }
-                byteval = inum.toShort()
-                wordval = null
-                floatval = null
-                asBoolean = byteval != 0.toShort()
-            }
-            DataType.BYTE -> {
-                val inum = num.toInt()
-                require(inum in -128..127) { "invalid value for byte: $inum" }
-                byteval = inum.toShort()
-                wordval = null
-                floatval = null
-                asBoolean = byteval != 0.toShort()
-            }
-            DataType.UWORD -> {
-                val inum = num.toInt()
-                require(inum in 0..65535) { "invalid value for uword: $inum" }
-                wordval = inum
-                byteval = null
-                floatval = null
-                asBoolean = wordval != 0
-            }
-            DataType.WORD -> {
-                val inum = num.toInt()
-                require(inum in -32768..32767) { "invalid value for word: $inum" }
-                wordval = inum
-                byteval = null
-                floatval = null
-                asBoolean = wordval != 0
-            }
-            DataType.FLOAT -> {
-                floatval = num.toDouble()
-                byteval = null
-                wordval = null
-                asBoolean = floatval != 0.0
-            }
-            else -> throw VmExecutionException("not a numeric value")
-        }
-    }
-
-    override fun toString(): String {
-        return when (type) {
-            DataType.UBYTE -> "ub:%02x".format(byteval)
-            DataType.BYTE -> {
-                if (byteval!! < 0)
-                    "b:-%02x".format(abs(byteval.toInt()))
-                else
-                    "b:%02x".format(byteval)
-            }
-            DataType.UWORD -> "uw:%04x".format(wordval)
-            DataType.WORD -> {
-                if (wordval!! < 0)
-                    "w:-%04x".format(abs(wordval))
-                else
-                    "w:%04x".format(wordval)
-            }
-            DataType.FLOAT -> "f:$floatval"
-            else -> "???"
-        }
-    }
-
-    override fun numericValue(): Number {
-        return when (type) {
-            in ByteDatatypes -> byteval!!
-            in WordDatatypes -> wordval!!
-            DataType.FLOAT -> floatval!!
-            else -> throw ArithmeticException("invalid datatype for numeric value: $type")
-        }
-    }
-
-    override fun integerValue(): Int {
-        return when (type) {
-            in ByteDatatypes -> byteval!!.toInt()
-            in WordDatatypes -> wordval!!
-            DataType.FLOAT -> throw ArithmeticException("float to integer loss of precision")
-            else -> throw ArithmeticException("invalid datatype for integer value: $type")
-        }
-    }
-
-    override fun hashCode(): Int = Objects.hash(byteval, wordval, floatval, type)
-
-    override fun equals(other: Any?): Boolean {
-        if (other == null || other !is RuntimeValueNumeric)
-            return false
-        return compareTo(other) == 0      // note: datatype doesn't matter
-    }
-
-    operator fun compareTo(other: RuntimeValueNumeric): Int = numericValue().toDouble().compareTo(other.numericValue().toDouble())
-
-    private fun arithResult(leftDt: DataType, result: Number, rightDt: DataType, op: String): RuntimeValueNumeric {
-        if (leftDt != rightDt)
-            throw ArithmeticException("left and right datatypes are not the same")
-        if (result.toDouble() < 0) {
-            return when (leftDt) {
-                DataType.UBYTE, DataType.UWORD -> {
-                    // storing a negative number in an unsigned one is done by storing the 2's complement instead
-                    val number = abs(result.toDouble().toInt())
-                    if (leftDt == DataType.UBYTE)
-                        RuntimeValueNumeric(DataType.UBYTE, (number xor 255) + 1)
-                    else
-                        RuntimeValueNumeric(DataType.UWORD, (number xor 65535) + 1)
-                }
-                DataType.BYTE -> {
-                    val v = result.toInt() and 255
-                    if (v < 128)
-                        RuntimeValueNumeric(DataType.BYTE, v)
-                    else
-                        RuntimeValueNumeric(DataType.BYTE, v - 256)
-                }
-                DataType.WORD -> {
-                    val v = result.toInt() and 65535
-                    if (v < 32768)
-                        RuntimeValueNumeric(DataType.WORD, v)
-                    else
-                        RuntimeValueNumeric(DataType.WORD, v - 65536)
-                }
-                DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, result)
-                else -> throw ArithmeticException("$op on non-numeric type")
-            }
-        }
-
-        return when (leftDt) {
-            DataType.UBYTE -> RuntimeValueNumeric(DataType.UBYTE, result.toInt() and 255)
-            DataType.BYTE -> {
-                val v = result.toInt() and 255
-                if (v < 128)
-                    RuntimeValueNumeric(DataType.BYTE, v)
-                else
-                    RuntimeValueNumeric(DataType.BYTE, v - 256)
-            }
-            DataType.UWORD -> RuntimeValueNumeric(DataType.UWORD, result.toInt() and 65535)
-            DataType.WORD -> {
-                val v = result.toInt() and 65535
-                if (v < 32768)
-                    RuntimeValueNumeric(DataType.WORD, v)
-                else
-                    RuntimeValueNumeric(DataType.WORD, v - 65536)
-            }
-            DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, result)
-            else -> throw ArithmeticException("$op on non-numeric type")
-        }
-    }
-
-    fun add(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        if (other.type == DataType.FLOAT && (type != DataType.FLOAT))
-            throw ArithmeticException("floating point loss of precision on type $type")
-        val v1 = numericValue()
-        val v2 = other.numericValue()
-        val result = v1.toDouble() + v2.toDouble()
-        return arithResult(type, result, other.type, "add")
-    }
-
-    fun sub(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        if (other.type == DataType.FLOAT && (type != DataType.FLOAT))
-            throw ArithmeticException("floating point loss of precision on type $type")
-        val v1 = numericValue()
-        val v2 = other.numericValue()
-        val result = v1.toDouble() - v2.toDouble()
-        return arithResult(type, result, other.type, "sub")
-    }
-
-    fun mul(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        if (other.type == DataType.FLOAT && (type != DataType.FLOAT))
-            throw ArithmeticException("floating point loss of precision on type $type")
-        val v1 = numericValue()
-        val v2 = other.numericValue()
-        val result = v1.toDouble() * v2.toDouble()
-        return arithResult(type, result, other.type, "mul")
-    }
-
-    fun div(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        if (other.type == DataType.FLOAT && (type != DataType.FLOAT))
-            throw ArithmeticException("floating point loss of precision on type $type")
-        val v1 = numericValue()
-        val v2 = other.numericValue()
-        if (v2.toDouble() == 0.0) {
-            when (type) {
-                DataType.UBYTE -> return RuntimeValueNumeric(DataType.UBYTE, 255)
-                DataType.BYTE -> return RuntimeValueNumeric(DataType.BYTE, 127)
-                DataType.UWORD -> return RuntimeValueNumeric(DataType.UWORD, 65535)
-                DataType.WORD -> return RuntimeValueNumeric(DataType.WORD, 32767)
-                else -> {
-                }
-            }
-        }
-        val result = v1.toDouble() / v2.toDouble()
-        // NOTE: integer division returns integer result!
-        return when (type) {
-            DataType.UBYTE -> RuntimeValueNumeric(DataType.UBYTE, result)
-            DataType.BYTE -> RuntimeValueNumeric(DataType.BYTE, result)
-            DataType.UWORD -> RuntimeValueNumeric(DataType.UWORD, result)
-            DataType.WORD -> RuntimeValueNumeric(DataType.WORD, result)
-            DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, result)
-            else -> throw ArithmeticException("div on non-numeric type")
-        }
-    }
-
-    fun remainder(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        val v1 = numericValue()
-        val v2 = other.numericValue()
-        val result = v1.toDouble() % v2.toDouble()
-        return arithResult(type, result, other.type, "remainder")
-    }
-
-    fun pow(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        val v1 = numericValue()
-        val v2 = other.numericValue()
-        val result = v1.toDouble().pow(v2.toDouble())
-        return arithResult(type, result, other.type, "pow")
-    }
-
-    fun shl(): RuntimeValueNumeric {
-        val v = integerValue()
-        return when (type) {
-            DataType.UBYTE -> RuntimeValueNumeric(type, (v shl 1) and 255)
-            DataType.UWORD -> RuntimeValueNumeric(type, (v shl 1) and 65535)
-            DataType.BYTE -> {
-                val value = v shl 1
-                if (value < 128)
-                    RuntimeValueNumeric(type, value)
-                else
-                    RuntimeValueNumeric(type, value - 256)
-            }
-            DataType.WORD -> {
-                val value = v shl 1
-                if (value < 32768)
-                    RuntimeValueNumeric(type, value)
-                else
-                    RuntimeValueNumeric(type, value - 65536)
-            }
-            else -> throw ArithmeticException("invalid type for shl: $type")
-        }
-    }
-
-    fun shr(): RuntimeValueNumeric {
-        val v = integerValue()
-        return when (type) {
-            DataType.UBYTE -> RuntimeValueNumeric(type, v ushr 1)
-            DataType.BYTE -> RuntimeValueNumeric(type, v shr 1)
-            DataType.UWORD -> RuntimeValueNumeric(type, v ushr 1)
-            DataType.WORD -> RuntimeValueNumeric(type, v shr 1)
-            else -> throw ArithmeticException("invalid type for shr: $type")
-        }
-    }
-
-    fun rol(carry: Boolean): Pair<RuntimeValueNumeric, Boolean> {
-        // 9 or 17 bit rotate left (with carry))
-        return when (type) {
-            DataType.UBYTE, DataType.BYTE -> {
-                val v = byteval!!.toInt()
-                val newCarry = (v and 0x80) != 0
-                val newval = (v and 0x7f shl 1) or (if (carry) 1 else 0)
-                Pair(RuntimeValueNumeric(DataType.UBYTE, newval), newCarry)
-            }
-            DataType.UWORD, DataType.WORD -> {
-                val v = wordval!!
-                val newCarry = (v and 0x8000) != 0
-                val newval = (v and 0x7fff shl 1) or (if (carry) 1 else 0)
-                Pair(RuntimeValueNumeric(DataType.UWORD, newval), newCarry)
-            }
-            else -> throw ArithmeticException("rol can only work on byte/word")
-        }
-    }
-
-    fun ror(carry: Boolean): Pair<RuntimeValueNumeric, Boolean> {
-        // 9 or 17 bit rotate right (with carry)
-        return when (type) {
-            DataType.UBYTE, DataType.BYTE -> {
-                val v = byteval!!.toInt()
-                val newCarry = v and 1 != 0
-                val newval = (v ushr 1) or (if (carry) 0x80 else 0)
-                Pair(RuntimeValueNumeric(DataType.UBYTE, newval), newCarry)
-            }
-            DataType.UWORD, DataType.WORD -> {
-                val v = wordval!!
-                val newCarry = v and 1 != 0
-                val newval = (v ushr 1) or (if (carry) 0x8000 else 0)
-                Pair(RuntimeValueNumeric(DataType.UWORD, newval), newCarry)
-            }
-            else -> throw ArithmeticException("ror2 can only work on byte/word")
-        }
-    }
-
-    fun rol2(): RuntimeValueNumeric {
-        // 8 or 16 bit rotate left
-        return when (type) {
-            DataType.UBYTE, DataType.BYTE -> {
-                val v = byteval!!.toInt()
-                val carry = (v and 0x80) ushr 7
-                val newval = (v and 0x7f shl 1) or carry
-                RuntimeValueNumeric(DataType.UBYTE, newval)
-            }
-            DataType.UWORD, DataType.WORD -> {
-                val v = wordval!!
-                val carry = (v and 0x8000) ushr 15
-                val newval = (v and 0x7fff shl 1) or carry
-                RuntimeValueNumeric(DataType.UWORD, newval)
-            }
-            else -> throw ArithmeticException("rol2 can only work on byte/word")
-        }
-    }
-
-    fun ror2(): RuntimeValueNumeric {
-        // 8 or 16 bit rotate right
-        return when (type) {
-            DataType.UBYTE, DataType.BYTE -> {
-                val v = byteval!!.toInt()
-                val carry = v and 1 shl 7
-                val newval = (v ushr 1) or carry
-                RuntimeValueNumeric(DataType.UBYTE, newval)
-            }
-            DataType.UWORD, DataType.WORD -> {
-                val v = wordval!!
-                val carry = v and 1 shl 15
-                val newval = (v ushr 1) or carry
-                RuntimeValueNumeric(DataType.UWORD, newval)
-            }
-            else -> throw ArithmeticException("ror2 can only work on byte/word")
-        }
-    }
-
-    fun neg(): RuntimeValueNumeric {
-        return when (type) {
-            DataType.BYTE -> RuntimeValueNumeric(DataType.BYTE, -(byteval!!))
-            DataType.WORD -> RuntimeValueNumeric(DataType.WORD, -(wordval!!))
-            DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, -(floatval)!!)
-            else -> throw ArithmeticException("neg can only work on byte/word/float")
-        }
-    }
-
-    fun abs(): RuntimeValueNumeric {
-        return when (type) {
-            DataType.BYTE -> RuntimeValueNumeric(DataType.BYTE, abs(byteval!!.toInt()))
-            DataType.WORD -> RuntimeValueNumeric(DataType.WORD, abs(wordval!!))
-            DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, abs(floatval!!))
-            else -> throw ArithmeticException("abs can only work on byte/word/float")
-        }
-    }
-
-    fun bitand(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        val v1 = integerValue()
-        val v2 = other.integerValue()
-        val result = v1 and v2
-        return RuntimeValueNumeric(type, result)
-    }
-
-    fun bitor(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        val v1 = integerValue()
-        val v2 = other.integerValue()
-        val result = v1 or v2
-        return RuntimeValueNumeric(type, result)
-    }
-
-    fun bitxor(other: RuntimeValueNumeric): RuntimeValueNumeric {
-        val v1 = integerValue()
-        val v2 = other.integerValue()
-        val result = v1 xor v2
-        return RuntimeValueNumeric(type, result)
-    }
-
-    fun and(other: RuntimeValueNumeric) = RuntimeValueNumeric(DataType.UBYTE, if (this.asBoolean && other.asBoolean) 1 else 0)
-    fun or(other: RuntimeValueNumeric) = RuntimeValueNumeric(DataType.UBYTE, if (this.asBoolean || other.asBoolean) 1 else 0)
-    fun xor(other: RuntimeValueNumeric) = RuntimeValueNumeric(DataType.UBYTE, if (this.asBoolean xor other.asBoolean) 1 else 0)
-    fun not() = RuntimeValueNumeric(DataType.UBYTE, if (this.asBoolean) 0 else 1)
-
-    fun inv(): RuntimeValueNumeric {
-        return when (type) {
-            DataType.UBYTE -> RuntimeValueNumeric(type, byteval!!.toInt().inv() and 255)
-            DataType.UWORD -> RuntimeValueNumeric(type, wordval!!.inv() and 65535)
-            DataType.BYTE -> RuntimeValueNumeric(type, byteval!!.toInt().inv())
-            DataType.WORD -> RuntimeValueNumeric(type, wordval!!.inv())
-            else -> throw ArithmeticException("inv can only work on byte/word")
-        }
-    }
-
-    fun inc(): RuntimeValueNumeric {
-        return when (type) {
-            DataType.UBYTE -> RuntimeValueNumeric(type, (byteval!! + 1) and 255)
-            DataType.UWORD -> RuntimeValueNumeric(type, (wordval!! + 1) and 65535)
-            DataType.BYTE -> {
-                val newval = byteval!! + 1
-                if (newval == 128)
-                    RuntimeValueNumeric(type, -128)
-                else
-                    RuntimeValueNumeric(type, newval)
-            }
-            DataType.WORD -> {
-                val newval = wordval!! + 1
-                if (newval == 32768)
-                    RuntimeValueNumeric(type, -32768)
-                else
-                    RuntimeValueNumeric(type, newval)
-            }
-            DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, floatval!! + 1)
-            else -> throw ArithmeticException("inc can only work on numeric types")
-        }
-    }
-
-    fun dec(): RuntimeValueNumeric {
-        return when (type) {
-            DataType.UBYTE -> RuntimeValueNumeric(type, (byteval!! - 1) and 255)
-            DataType.UWORD -> RuntimeValueNumeric(type, (wordval!! - 1) and 65535)
-            DataType.BYTE -> {
-                val newval = byteval!! - 1
-                if (newval == -129)
-                    RuntimeValueNumeric(type, 127)
-                else
-                    RuntimeValueNumeric(type, newval)
-            }
-            DataType.WORD -> {
-                val newval = wordval!! - 1
-                if (newval == -32769)
-                    RuntimeValueNumeric(type, 32767)
-                else
-                    RuntimeValueNumeric(type, newval)
-            }
-            DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, floatval!! - 1)
-            else -> throw ArithmeticException("dec can only work on numeric types")
-        }
-    }
-
-    fun msb(): RuntimeValueNumeric {
-        return when (type) {
-            in ByteDatatypes -> RuntimeValueNumeric(DataType.UBYTE, 0)
-            in WordDatatypes -> RuntimeValueNumeric(DataType.UBYTE, wordval!! ushr 8 and 255)
-            else -> throw ArithmeticException("msb can only work on (u)byte/(u)word")
-        }
-    }
-
-    fun cast(targetType: DataType): RuntimeValueNumeric {
-        return when (type) {
-            DataType.UBYTE -> {
-                when (targetType) {
-                    DataType.UBYTE -> this
-                    DataType.BYTE -> {
-                        val nval = byteval!!.toInt()
-                        if (nval < 128)
-                            RuntimeValueNumeric(DataType.BYTE, nval)
-                        else
-                            RuntimeValueNumeric(DataType.BYTE, nval - 256)
-                    }
-                    DataType.UWORD -> RuntimeValueNumeric(DataType.UWORD, numericValue())
-                    DataType.WORD -> {
-                        val nval = numericValue().toInt()
-                        if (nval < 32768)
-                            RuntimeValueNumeric(DataType.WORD, nval)
-                        else
-                            RuntimeValueNumeric(DataType.WORD, nval - 65536)
-                    }
-                    DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, numericValue())
-                    else -> throw ArithmeticException("invalid type cast from $type to $targetType")
-                }
-            }
-            DataType.BYTE -> {
-                when (targetType) {
-                    DataType.BYTE -> this
-                    DataType.UBYTE -> RuntimeValueNumeric(DataType.UBYTE, integerValue() and 255)
-                    DataType.UWORD -> RuntimeValueNumeric(DataType.UWORD, integerValue() and 65535)
-                    DataType.WORD -> RuntimeValueNumeric(DataType.WORD, integerValue())
-                    DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, numericValue())
-                    else -> throw ArithmeticException("invalid type cast from $type to $targetType")
-                }
-            }
-            DataType.UWORD -> {
-                when (targetType) {
-                    DataType.BYTE -> {
-                        val v = integerValue()
-                        if (v < 128)
-                            RuntimeValueNumeric(DataType.BYTE, v)
-                        else
-                            RuntimeValueNumeric(DataType.BYTE, v - 256)
-                    }
-                    DataType.UBYTE -> RuntimeValueNumeric(DataType.UBYTE, integerValue() and 255)
-                    DataType.UWORD -> this
-                    DataType.WORD -> {
-                        val v = integerValue()
-                        if (v < 32768)
-                            RuntimeValueNumeric(DataType.WORD, v)
-                        else
-                            RuntimeValueNumeric(DataType.WORD, v - 65536)
-                    }
-                    DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, numericValue())
-                    else -> throw ArithmeticException("invalid type cast from $type to $targetType")
-                }
-            }
-            DataType.WORD -> {
-                when (targetType) {
-                    DataType.BYTE -> {
-                        val v = integerValue() and 255
-                        if (v < 128)
-                            RuntimeValueNumeric(DataType.BYTE, v)
-                        else
-                            RuntimeValueNumeric(DataType.BYTE, v - 256)
-                    }
-                    DataType.UBYTE -> RuntimeValueNumeric(DataType.UBYTE, integerValue() and 65535)
-                    DataType.UWORD -> RuntimeValueNumeric(DataType.UWORD, integerValue())
-                    DataType.WORD -> this
-                    DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, numericValue())
-                    else -> throw ArithmeticException("invalid type cast from $type to $targetType")
-                }
-            }
-            DataType.FLOAT -> {
-                when (targetType) {
-                    DataType.BYTE -> {
-                        val integer = numericValue().toInt()
-                        if (integer in -128..127)
-                            RuntimeValueNumeric(DataType.BYTE, integer)
-                        else
-                            throw ArithmeticException("overflow when casting float to byte: $this")
-                    }
-                    DataType.UBYTE -> RuntimeValueNumeric(DataType.UBYTE, numericValue().toInt())
-                    DataType.UWORD -> RuntimeValueNumeric(DataType.UWORD, numericValue().toInt())
-                    DataType.WORD -> {
-                        val integer = numericValue().toInt()
-                        if (integer in -32768..32767)
-                            RuntimeValueNumeric(DataType.WORD, integer)
-                        else
-                            throw ArithmeticException("overflow when casting float to word: $this")
-                    }
-                    DataType.FLOAT -> this
-                    else -> throw ArithmeticException("invalid type cast from $type to $targetType")
-                }
-            }
-            else -> throw ArithmeticException("invalid type cast from $type to $targetType")
-        }
-    }
-}
-
-
-class RuntimeValueString(val str: String, val altEncoding: Boolean, val heapId: Int?): RuntimeValueBase(DataType.STR) {
-    companion object {
-        fun fromLv(string: StringLiteralValue): RuntimeValueString {
-            return RuntimeValueString(string.value, string.altEncoding, string.heapId)
-        }
-    }
-
-    override fun toString(): String = if(type==DataType.STR) "str:$str"  else "???"
-
-    override fun hashCode(): Int = Objects.hash(type, str)
-
-    override fun equals(other: Any?): Boolean {
-        if (other == null || other !is RuntimeValueString)
-            return false
-        return type == other.type && str == other.str
-    }
-
-    fun iterator(): Iterator<Number> = str.map { it.toShort() }.iterator()
-
-    override fun numericValue(): Number {
-        throw VmExecutionException("string is not a number")
-    }
-
-    override fun integerValue(): Int {
-        throw VmExecutionException("string is not a number")
-    }
-}
-
-
-open class RuntimeValueArray(type: DataType, val array: Array<Number>, val heapId: Int?): RuntimeValueBase(type) {
-
-    companion object {
-        fun fromLv(array: ArrayLiteralValue): RuntimeValueArray {
-            return if (array.type.istype(DataType.ARRAY_F)) {
-                val doubleArray = array.value.map { (it as NumericLiteralValue).number }.toTypedArray()
-                RuntimeValueArray(DataType.ARRAY_F, doubleArray, array.heapId)
-            } else {
-                val resultArray = mutableListOf<Number>()
-                for (elt in array.value.withIndex()) {
-                    if (elt.value is NumericLiteralValue)
-                        resultArray.add((elt.value as NumericLiteralValue).number.toInt())
-                    else {
-                        resultArray.add((elt.hashCode()))  // ...poor man's implementation of ADDRESSOF(array), it probably won't work very well
-                    }
-                }
-                RuntimeValueArray(array.type.typeOrElse(DataType.STRUCT), resultArray.toTypedArray(), array.heapId)
-            }
-        }
-    }
-
-    override fun toString(): String {
-        return when (type) {
-            DataType.ARRAY_UB -> "array_ub:..."
-            DataType.ARRAY_B -> "array_b:..."
-            DataType.ARRAY_UW -> "array_uw:..."
-            DataType.ARRAY_W -> "array_w:..."
-            DataType.ARRAY_F -> "array_f:..."
-            else -> "???"
-        }
-    }
-
-    override fun hashCode(): Int = Objects.hash(type, array)
-
-    override fun equals(other: Any?): Boolean {
-        if (other == null || other !is RuntimeValueArray)
-            return false
-        return type == other.type && array.contentEquals(other.array)
-    }
-
-    open fun iterator(): Iterator<Number> = array.iterator()
-
-    override fun numericValue(): Number {
-        throw VmExecutionException("array is not a number")
-    }
-
-    override fun integerValue(): Int {
-        throw VmExecutionException("array is not a number")
-    }
-}
-
-
-class RuntimeValueRange(type: DataType, val range: IntProgression): RuntimeValueArray(type, range.toList().toTypedArray(), null) {
-    override fun iterator(): Iterator<Number> {
-        return range.iterator()
-    }
-}
@@ -1,177 +0,0 @@
-package prog8.vm.astvm
-
-import prog8.ast.Program
-import prog8.ast.base.ArrayElementTypes
-import prog8.ast.base.DataType
-import prog8.ast.base.FatalAstException
-import prog8.ast.base.VarDeclType
-import prog8.ast.expressions.*
-import prog8.ast.statements.BuiltinFunctionStatementPlaceholder
-import prog8.ast.statements.Label
-import prog8.ast.statements.Subroutine
-import prog8.ast.statements.VarDecl
-import prog8.vm.*
-
-
-typealias BuiltinfunctionCaller =  (name: String, args: List<RuntimeValueNumeric>, flags: StatusFlags) -> RuntimeValueNumeric?
-typealias SubroutineCaller =  (sub: Subroutine, args: List<RuntimeValueNumeric>, startAtLabel: Label?) -> RuntimeValueNumeric?
-
-
-class EvalContext(val program: Program, val mem: Memory, val statusflags: StatusFlags,
-                  val runtimeVars: RuntimeVariables,
-                  val performBuiltinFunction: BuiltinfunctionCaller,
-                  val executeSubroutine: SubroutineCaller)
-
-fun evaluate(expr: Expression, ctx: EvalContext): RuntimeValueBase {
-    val constval = expr.constValue(ctx.program)
-    if(constval!=null)
-        return RuntimeValueNumeric.fromLv(constval)
-
-    when(expr) {
-        is NumericLiteralValue -> return RuntimeValueNumeric.fromLv(expr)
-        is StringLiteralValue -> return RuntimeValueString.fromLv(expr)
-        is ArrayLiteralValue -> return RuntimeValueArray.fromLv(expr)
-        is PrefixExpression -> {
-            return when(expr.operator) {
-                "-" -> (evaluate(expr.expression, ctx) as RuntimeValueNumeric).neg()
-                "~" -> (evaluate(expr.expression, ctx) as RuntimeValueNumeric).inv()
-                "not" -> (evaluate(expr.expression, ctx) as RuntimeValueNumeric).not()
-                // unary '+' should have been optimized away
-                else -> throw VmExecutionException("unsupported prefix operator "+expr.operator)
-            }
-        }
-        is BinaryExpression -> {
-            val left = evaluate(expr.left, ctx) as RuntimeValueNumeric
-            val right = evaluate(expr.right, ctx) as RuntimeValueNumeric
-            return when(expr.operator) {
-                "<" -> RuntimeValueNumeric(DataType.UBYTE, if (left < right) 1 else 0)
-                "<=" -> RuntimeValueNumeric(DataType.UBYTE, if (left <= right) 1 else 0)
-                ">" -> RuntimeValueNumeric(DataType.UBYTE, if (left > right) 1 else 0)
-                ">=" -> RuntimeValueNumeric(DataType.UBYTE, if (left >= right) 1 else 0)
-                "==" -> RuntimeValueNumeric(DataType.UBYTE, if (left == right) 1 else 0)
-                "!=" -> RuntimeValueNumeric(DataType.UBYTE, if (left != right) 1 else 0)
-                "+" -> left.add(right)
-                "-" -> left.sub(right)
-                "*" -> left.mul(right)
-                "/" -> left.div(right)
-                "**" -> left.pow(right)
-                "<<" -> {
-                    var result = left
-                    repeat(right.integerValue()) {result = result.shl()}
-                    result
-                }
-                ">>" -> {
-                    var result = left
-                    repeat(right.integerValue()) {result = result.shr()}
-                    result
-                }
-                "%" -> left.remainder(right)
-                "|" -> left.bitor(right)
-                "&" -> left.bitand(right)
-                "^" -> left.bitxor(right)
-                "and" -> left.and(right)
-                "or" -> left.or(right)
-                "xor" -> left.xor(right)
-                else -> throw VmExecutionException("unsupported operator "+expr.operator)
-            }
-        }
-        is ArrayIndexedExpression -> {
-            val array = evaluate(expr.identifier, ctx)
-            val index = evaluate(expr.arrayspec.index, ctx) as RuntimeValueNumeric
-            return when (array) {
-                is RuntimeValueString -> {
-                    val value = array.str[index.integerValue()]
-                    RuntimeValueNumeric(ArrayElementTypes.getValue(array.type), value.toShort())
-                }
-                is RuntimeValueArray -> {
-                    val value = array.array[index.integerValue()]
-                    RuntimeValueNumeric(ArrayElementTypes.getValue(array.type), value)
-                }
-                else -> throw VmExecutionException("weird type")
-            }
-        }
-        is TypecastExpression -> {
-            return (evaluate(expr.expression, ctx) as RuntimeValueNumeric).cast(expr.type)
-        }
-        is AddressOf -> {
-            // we support: address of heap var -> the heap id
-            return try {
-                val heapId = expr.identifier.heapId(ctx.program.namespace)
-                RuntimeValueNumeric(DataType.UWORD, heapId)
-            } catch( f: FatalAstException) {
-                // fallback: use the hash of the name, so we have at least *a* value...
-                val address = expr.identifier.hashCode() and 65535
-                RuntimeValueNumeric(DataType.UWORD, address)
-            }
-        }
-        is DirectMemoryRead -> {
-            val address = (evaluate(expr.addressExpression, ctx) as RuntimeValueNumeric).wordval!!
-            return RuntimeValueNumeric(DataType.UBYTE, ctx.mem.getUByte(address))
-        }
-        is RegisterExpr -> return ctx.runtimeVars.get(ctx.program.namespace, expr.register.name)
-        is IdentifierReference -> {
-            val scope = expr.definingScope()
-            val variable = scope.lookup(expr.nameInSource, expr)
-            if(variable is VarDecl) {
-                when {
-                    variable.type==VarDeclType.VAR -> return ctx.runtimeVars.get(variable.definingScope(), variable.name)
-                    variable.datatype==DataType.STRUCT -> throw VmExecutionException("cannot process structs by-value.  at ${expr.position}")
-                    else -> {
-                        val address = ctx.runtimeVars.getMemoryAddress(variable.definingScope(), variable.name)
-                        return when(variable.datatype) {
-                            DataType.UBYTE -> RuntimeValueNumeric(DataType.UBYTE, ctx.mem.getUByte(address))
-                            DataType.BYTE -> RuntimeValueNumeric(DataType.BYTE, ctx.mem.getSByte(address))
-                            DataType.UWORD -> RuntimeValueNumeric(DataType.UWORD, ctx.mem.getUWord(address))
-                            DataType.WORD -> RuntimeValueNumeric(DataType.WORD, ctx.mem.getSWord(address))
-                            DataType.FLOAT -> RuntimeValueNumeric(DataType.FLOAT, ctx.mem.getFloat(address))
-                            DataType.STR -> RuntimeValueString(ctx.mem.getString(address, false), false, null)
-                            else -> throw VmExecutionException("unexpected datatype $variable")
-                        }
-                    }
-                }
-            } else
-                throw VmExecutionException("weird identifier reference $variable")
-        }
-        is FunctionCall -> {
-            val sub = expr.target.targetStatement(ctx.program.namespace)
-            val args = expr.args.map { evaluate(it, ctx) as RuntimeValueNumeric }
-            return when(sub) {
-                is Subroutine -> {
-                    val result = ctx.executeSubroutine(sub, args, null)
-                            ?: throw VmExecutionException("expected a result from functioncall $expr")
-                    result
-                }
-                is BuiltinFunctionStatementPlaceholder -> {
-                    val result = ctx.performBuiltinFunction(sub.name, args, ctx.statusflags)
-                            ?: throw VmExecutionException("expected 1 result from functioncall $expr")
-                    result
-                }
-                else -> {
-                    throw VmExecutionException("unimplemented function call target $sub")
-                }
-            }
-        }
-        is RangeExpr -> {
-            val cRange = expr.toConstantIntegerRange()
-            if(cRange!=null) {
-                val dt = expr.inferType(ctx.program)
-                if(dt.isKnown)
-                    return RuntimeValueRange(dt.typeOrElse(DataType.UBYTE), cRange)
-                else
-                    throw VmExecutionException("couldn't determine datatype")
-            }
-            val fromVal = (evaluate(expr.from, ctx) as RuntimeValueNumeric).integerValue()
-            val toVal = (evaluate(expr.to, ctx) as RuntimeValueNumeric).integerValue()
-            val stepVal = (evaluate(expr.step, ctx) as RuntimeValueNumeric).integerValue()
-            val range = makeRange(fromVal, toVal, stepVal)
-            val dt = expr.inferType(ctx.program)
-            if(dt.isKnown)
-                return RuntimeValueRange(dt.typeOrElse(DataType.UBYTE), range)
-            else
-                throw VmExecutionException("couldn't determine datatype")
-        }
-        else -> {
-            throw VmExecutionException("unimplemented expression node $expr")
-        }
-    }
-}
@@ -1,122 +0,0 @@
-package prog8.vm.astvm
-
-import prog8.compiler.target.CompilationTarget
-import prog8.compiler.target.c64.C64MachineDefinition
-import kotlin.math.abs
-
-class Memory(private val readObserver: (address: Int, value: Short) -> Short,
-             private val writeObserver: (address: Int, value: Short) -> Short)
-{
-
-    private val mem = ShortArray(65536)         // shorts because byte is signed and we store values 0..255
-    private val observed = BooleanArray(65536)     // what addresses are observed
-
-
-    fun observe(vararg address: Int) {
-        address.forEach { observed[it]=true }
-    }
-
-    fun getUByte(address: Int): Short {
-        return if(observed[address]) readObserver(address, mem[address])
-        else mem[address]
-    }
-
-    fun getUByteDirectly(address: Int): Short {
-        return mem[address]
-    }
-
-    fun getSByte(address: Int): Short {
-        val ubyte = getUByte(address)
-        return if(ubyte <= 127) ubyte
-        else (-((ubyte.toInt() xor 255)+1)).toShort()   // 2's complement
-    }
-
-    fun setUByte(address: Int, value: Short) {
-        if(value !in 0..255)
-            throw VmExecutionException("ubyte value out of range $value")
-        mem[address] =
-                if(observed[address]) writeObserver(address, value)
-                else value
-    }
-
-    fun setUByteDirectly(address: Int, value: Short) {
-        if(value !in 0..255)
-            throw VmExecutionException("ubyte value out of range $value")
-        mem[address] = value
-    }
-
-    fun setSByte(address: Int, value: Short) {
-        if(value !in -128..127) throw VmExecutionException("byte value out of range $value")
-        val ubyte =
-                if(value>=0) value
-                else ((abs(value.toInt()) xor 255)+1).toShort()        // 2's complement
-        setUByte(address, ubyte)
-    }
-
-    fun getUWord(address: Int): Int {
-        return getUByte(address) + 256*getUByte(address+1)
-    }
-
-    fun getSWord(address: Int): Int {
-        val uword = getUWord(address)
-        if(uword <= 32767)
-            return uword
-        return -((uword xor 65535)+1)   // 2's complement
-    }
-
-    fun setUWord(address: Int, value: Int) {
-        if(value !in 0..65535)
-            throw VmExecutionException("uword value out of range $value")
-        setUByte(address, value.and(255).toShort())
-        setUByte(address+1, (value / 256).toShort())
-    }
-
-    fun setSWord(address: Int, value: Int) {
-        if(value !in -32768..32767) throw VmExecutionException("word value out of range $value")
-        if(value>=0)
-            setUWord(address, value)
-        else
-            setUWord(address, (abs(value) xor 65535)+1)        // 2's complement
-    }
-
-    fun setFloat(address: Int, value: Double) {
-        val mflpt5 = C64MachineDefinition.Mflpt5.fromNumber(value)
-        setUByte(address, mflpt5.b0)
-        setUByte(address+1, mflpt5.b1)
-        setUByte(address+2, mflpt5.b2)
-        setUByte(address+3, mflpt5.b3)
-        setUByte(address+4, mflpt5.b4)
-    }
-
-    fun getFloat(address: Int): Double {
-        return C64MachineDefinition.Mflpt5(getUByte(address), getUByte(address + 1), getUByte(address + 2),
-                getUByte(address + 3), getUByte(address + 4)).toDouble()
-    }
-
-    fun setString(address: Int, str: String, altEncoding: Boolean) {
-        val encoded = CompilationTarget.encodeString(str, altEncoding)
-        var addr = address
-        for (c in encoded) setUByte(addr++, c)
-        setUByte(addr, 0)
-    }
-
-    fun getString(strAddress: Int, altEncoding: Boolean): String {
-        val encoded = mutableListOf<Short>()
-        var addr = strAddress
-        while(true) {
-            val byte = getUByte(addr++)
-            if(byte==0.toShort()) break
-            encoded.add(byte)
-        }
-        return CompilationTarget.decodeString(encoded, altEncoding)
-    }
-
-    fun clear() {
-        for(i in 0..65535) setUByte(i, 0)
-    }
-
-    fun copy(from: Int, to: Int, numbytes: Int) {
-        for(i in 0 until numbytes)
-            setUByte(to+i, getUByte(from+i))
-    }
-}
@@ -1,184 +0,0 @@
-package prog8.vm.astvm
-
-import prog8.compiler.target.c64.C64MachineDefinition
-import prog8.compiler.target.c64.Petscii
-import java.awt.*
-import java.awt.event.KeyEvent
-import java.awt.event.KeyListener
-import java.awt.image.BufferedImage
-import java.util.*
-import javax.swing.JFrame
-import javax.swing.JPanel
-import javax.swing.Timer
-
-
-class BitmapScreenPanel : KeyListener, JPanel() {
-
-    private val image = BufferedImage(SCREENWIDTH, SCREENHEIGHT, BufferedImage.TYPE_INT_ARGB)
-    private val g2d = image.graphics as Graphics2D
-    private var cursorX: Int=0
-    private var cursorY: Int=0
-    val keyboardBuffer = ArrayDeque<Char>()
-
-    init {
-        val size = Dimension(image.width * SCALING, image.height * SCALING)
-        minimumSize = size
-        maximumSize = size
-        preferredSize = size
-        clearScreen(6)
-        isFocusable = true
-        requestFocusInWindow()
-        addKeyListener(this)
-    }
-
-    override fun keyTyped(p0: KeyEvent) {
-        keyboardBuffer.add(p0.keyChar)
-    }
-
-    override fun keyPressed(p0: KeyEvent) {
-    }
-
-    override fun keyReleased(p0: KeyEvent?) {
-    }
-
-    override fun paint(graphics: Graphics?) {
-        val g2d = graphics as Graphics2D?
-        g2d!!.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_OFF)
-        g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_DISABLE)
-        g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_NEAREST_NEIGHBOR)
-        g2d.drawImage(image, 0, 0, image.width * 3, image.height * 3, null)
-    }
-
-    fun clearScreen(color: Short) {
-        g2d.background = C64MachineDefinition.colorPalette[color % C64MachineDefinition.colorPalette.size]
-        g2d.clearRect(0, 0, SCREENWIDTH, SCREENHEIGHT)
-        cursorX = 0
-        cursorY = 0
-    }
-    fun setPixel(x: Int, y: Int, color: Short) {
-        image.setRGB(x, y, C64MachineDefinition.colorPalette[color % C64MachineDefinition.colorPalette.size].rgb)
-    }
-    fun drawLine(x1: Int, y1: Int, x2: Int, y2: Int, color: Short) {
-        g2d.color = C64MachineDefinition.colorPalette[color % C64MachineDefinition.colorPalette.size]
-        g2d.drawLine(x1, y1, x2, y2)
-    }
-
-    fun printAsciiText(text: String) {
-        val t2 = text.substringBefore(0.toChar())
-        val petscii = Petscii.encodePetscii(t2, true)
-        petscii.forEach { printPetsciiChar(it) }
-    }
-
-    fun printPetsciiChar(petscii: Short) {
-        if(petscii in listOf(0x0d.toShort(), 0x8d.toShort())) {
-            // Return and shift-Return
-            cursorX=0
-            cursorY++
-        } else {
-            val scr = Petscii.petscii2scr(petscii, false)
-            setScreenChar(cursorX, cursorY, scr, 1)
-            cursorX++
-            if (cursorX >= (SCREENWIDTH / 8)) {
-                cursorY++
-                cursorX = 0
-            }
-        }
-        while(cursorY>=(SCREENHEIGHT/8)) {
-            // scroll the screen up because the cursor went past the last line
-            Thread.sleep(10)
-            val screen = image.copy()
-            val graphics = image.graphics as Graphics2D
-            graphics.drawImage(screen, 0, -8, null)
-            val color = graphics.color
-            graphics.color = C64MachineDefinition.colorPalette[6]
-            graphics.fillRect(0, 24*8, SCREENWIDTH, 25*8)
-            graphics.color=color
-            cursorY--
-        }
-    }
-
-    fun setScreenChar(x: Int, y: Int, screencode: Short, color: Short) {
-        g2d.clearRect(8*x, 8*y, 8, 8)
-        val colorIdx = (color % C64MachineDefinition.colorPalette.size).toShort()
-        val coloredImage = C64MachineDefinition.Charset.getColoredChar(screencode, colorIdx)
-        g2d.drawImage(coloredImage, 8*x, 8*y , null)
-    }
-
-    fun setCursorPos(x: Int, y: Int) {
-        cursorX = x
-        cursorY = y
-    }
-
-    fun getCursorPos(): Pair<Int, Int> {
-        return Pair(cursorX, cursorY)
-    }
-
-    companion object {
-        const val SCREENWIDTH = 320
-        const val SCREENHEIGHT = 200
-        const val SCALING = 3
-    }
-}
-
-
-class ScreenDialog(title: String) : JFrame(title) {
-    val canvas = BitmapScreenPanel()
-    val keyboardBuffer = canvas.keyboardBuffer
-
-    init {
-        val borderWidth = 16
-        layout = GridBagLayout()
-        defaultCloseOperation = EXIT_ON_CLOSE
-        isResizable = false
-
-        // the borders (top, left, right, bottom)
-        val borderTop = JPanel().apply {
-            preferredSize = Dimension(BitmapScreenPanel.SCALING * (BitmapScreenPanel.SCREENWIDTH +2*borderWidth), BitmapScreenPanel.SCALING * borderWidth)
-            background = C64MachineDefinition.colorPalette[14]
-        }
-        val borderBottom = JPanel().apply {
-            preferredSize =Dimension(BitmapScreenPanel.SCALING * (BitmapScreenPanel.SCREENWIDTH +2*borderWidth), BitmapScreenPanel.SCALING * borderWidth)
-            background = C64MachineDefinition.colorPalette[14]
-        }
-        val borderLeft = JPanel().apply {
-            preferredSize =Dimension(BitmapScreenPanel.SCALING * borderWidth, BitmapScreenPanel.SCALING * BitmapScreenPanel.SCREENHEIGHT)
-            background = C64MachineDefinition.colorPalette[14]
-        }
-        val borderRight = JPanel().apply {
-            preferredSize =Dimension(BitmapScreenPanel.SCALING * borderWidth, BitmapScreenPanel.SCALING * BitmapScreenPanel.SCREENHEIGHT)
-            background = C64MachineDefinition.colorPalette[14]
-        }
-        var c = GridBagConstraints()
-        c.gridx=0; c.gridy=1; c.gridwidth=3
-        add(borderTop, c)
-        c = GridBagConstraints()
-        c.gridx=0; c.gridy=2
-        add(borderLeft, c)
-        c = GridBagConstraints()
-        c.gridx=2; c.gridy=2
-        add(borderRight, c)
-        c = GridBagConstraints()
-        c.gridx=0; c.gridy=3; c.gridwidth=3
-        add(borderBottom, c)
-        // the screen canvas(bitmap)
-        c = GridBagConstraints()
-        c.gridx = 1; c.gridy = 2
-        add(canvas, c)
-
-        canvas.requestFocusInWindow()
-    }
-
-    fun start() {
-        val repaintTimer = Timer(1000 / 60) { repaint() }
-        repaintTimer.start()
-    }
-}
-
-
-private fun BufferedImage.copy(): BufferedImage {
-    val bcopy = BufferedImage(this.width, this.height, this.type)
-    val g = bcopy.graphics
-    g.drawImage(this, 0, 0, null)
-    g.dispose()
-    return bcopy
-}
@@ -1,80 +0,0 @@
-package prog8.vm.astvm
-
-import prog8.ast.Program
-import prog8.ast.base.DataType
-import prog8.ast.base.Position
-import prog8.ast.base.Register
-import prog8.ast.base.VarDeclType
-import prog8.ast.expressions.ArrayLiteralValue
-import prog8.ast.expressions.NumericLiteralValue
-import prog8.ast.expressions.StringLiteralValue
-import prog8.ast.processing.IAstModifyingVisitor
-import prog8.ast.statements.Statement
-import prog8.ast.statements.StructDecl
-import prog8.ast.statements.VarDecl
-import prog8.ast.statements.ZeropageWish
-import prog8.vm.RuntimeValueArray
-import prog8.vm.RuntimeValueNumeric
-import prog8.vm.RuntimeValueString
-
-class VariablesCreator(private val runtimeVariables: RuntimeVariables) : IAstModifyingVisitor {
-
-    override fun visit(program: Program) {
-        // define the three registers as global variables
-        runtimeVariables.define(program.namespace, Register.A.name, RuntimeValueNumeric(DataType.UBYTE, 0))
-        runtimeVariables.define(program.namespace, Register.X.name, RuntimeValueNumeric(DataType.UBYTE, 255))
-        runtimeVariables.define(program.namespace, Register.Y.name, RuntimeValueNumeric(DataType.UBYTE, 0))
-
-        val globalpos = Position("<<global>>", 0, 0, 0)
-        val vdA = VarDecl(VarDeclType.VAR, DataType.UBYTE, ZeropageWish.DONTCARE, null, Register.A.name, null,
-                NumericLiteralValue.optimalInteger(0, globalpos), isArray = false, autogeneratedDontRemove = true, position = globalpos)
-        val vdX = VarDecl(VarDeclType.VAR, DataType.UBYTE, ZeropageWish.DONTCARE, null, Register.X.name, null,
-                NumericLiteralValue.optimalInteger(255, globalpos), isArray = false, autogeneratedDontRemove = true, position = globalpos)
-        val vdY = VarDecl(VarDeclType.VAR, DataType.UBYTE, ZeropageWish.DONTCARE, null, Register.Y.name, null,
-                NumericLiteralValue.optimalInteger(0, globalpos), isArray = false, autogeneratedDontRemove = true, position = globalpos)
-        vdA.linkParents(program.namespace)
-        vdX.linkParents(program.namespace)
-        vdY.linkParents(program.namespace)
-        program.namespace.statements.add(vdA)
-        program.namespace.statements.add(vdX)
-        program.namespace.statements.add(vdY)
-
-        super.visit(program)
-    }
-
-    override fun visit(decl: VarDecl): Statement {
-        // if the decl is part of a struct, just skip it
-        if(decl.parent !is StructDecl) {
-            when (decl.type) {
-                VarDeclType.VAR -> {
-                    if(decl.datatype!=DataType.STRUCT) {
-                        val numericLv = decl.value as? NumericLiteralValue
-                        val value = if(numericLv!=null) {
-                            RuntimeValueNumeric.fromLv(numericLv)
-                        } else {
-                            val strLv = decl.value as? StringLiteralValue
-                            val arrayLv = decl.value as? ArrayLiteralValue
-                            when {
-                                strLv!=null -> {
-                                    RuntimeValueString.fromLv(strLv)
-                                }
-                                arrayLv!=null -> {
-                                    RuntimeValueArray.fromLv(arrayLv)
-                                }
-                                else -> throw VmExecutionException("weird var type")
-                            }
-                        }
-                        runtimeVariables.define(decl.definingScope(), decl.name, value)
-                    }
-                }
-                VarDeclType.MEMORY -> {
-                    runtimeVariables.defineMemory(decl.definingScope(), decl.name, (decl.value as NumericLiteralValue).number.toInt())
-                }
-                VarDeclType.CONST -> {
-                    // consts should have been const-folded away
-                }
-            }
-        }
-        return super.visit(decl)
-    }
-}
@@ -1,352 +0,0 @@
-package prog8tests
-
-import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.TestInstance
-import prog8.ast.base.DataType
-import prog8.vm.RuntimeValueNumeric
-import kotlin.test.*
-
-
-private fun sameValueAndType(v1: RuntimeValueNumeric, v2: RuntimeValueNumeric): Boolean {
-    return v1.type==v2.type && v1==v2
-}
-
-
-@TestInstance(TestInstance.Lifecycle.PER_CLASS)
-class TestRuntimeValueNumeric {
-
-    @Test
-    fun testValueRanges() {
-        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 0).integerValue())
-        assertEquals(255, RuntimeValueNumeric(DataType.UBYTE, 255).integerValue())
-        assertFailsWith<IllegalArgumentException> { RuntimeValueNumeric(DataType.UBYTE, -1)}
-        assertFailsWith<IllegalArgumentException> { RuntimeValueNumeric(DataType.UBYTE, 256)}
-
-        assertEquals(0, RuntimeValueNumeric(DataType.BYTE, 0).integerValue())
-        assertEquals(-128, RuntimeValueNumeric(DataType.BYTE, -128).integerValue())
-        assertEquals(127, RuntimeValueNumeric(DataType.BYTE, 127).integerValue())
-        assertFailsWith<IllegalArgumentException> { RuntimeValueNumeric(DataType.BYTE, -129)}
-        assertFailsWith<IllegalArgumentException> { RuntimeValueNumeric(DataType.BYTE, 128)}
-
-        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 0).integerValue())
-        assertEquals(65535, RuntimeValueNumeric(DataType.UWORD, 65535).integerValue())
-        assertFailsWith<IllegalArgumentException> { RuntimeValueNumeric(DataType.UWORD, -1)}
-        assertFailsWith<IllegalArgumentException> { RuntimeValueNumeric(DataType.UWORD, 65536)}
-
-        assertEquals(0, RuntimeValueNumeric(DataType.WORD, 0).integerValue())
-        assertEquals(-32768, RuntimeValueNumeric(DataType.WORD, -32768).integerValue())
-        assertEquals(32767, RuntimeValueNumeric(DataType.WORD, 32767).integerValue())
-        assertFailsWith<IllegalArgumentException> { RuntimeValueNumeric(DataType.WORD, -32769)}
-        assertFailsWith<IllegalArgumentException> { RuntimeValueNumeric(DataType.WORD, 32768)}
-    }
-
-    @Test
-    fun testTruthiness()
-    {
-        assertFalse(RuntimeValueNumeric(DataType.BYTE, 0).asBoolean)
-        assertFalse(RuntimeValueNumeric(DataType.UBYTE, 0).asBoolean)
-        assertFalse(RuntimeValueNumeric(DataType.WORD, 0).asBoolean)
-        assertFalse(RuntimeValueNumeric(DataType.UWORD, 0).asBoolean)
-        assertFalse(RuntimeValueNumeric(DataType.FLOAT, 0.0).asBoolean)
-
-        assertTrue(RuntimeValueNumeric(DataType.BYTE, 42).asBoolean)
-        assertTrue(RuntimeValueNumeric(DataType.UBYTE, 42).asBoolean)
-        assertTrue(RuntimeValueNumeric(DataType.WORD, 42).asBoolean)
-        assertTrue(RuntimeValueNumeric(DataType.UWORD, 42).asBoolean)
-        assertTrue(RuntimeValueNumeric(DataType.FLOAT, 42.0).asBoolean)
-        assertTrue(RuntimeValueNumeric(DataType.BYTE, -42).asBoolean)
-        assertTrue(RuntimeValueNumeric(DataType.WORD, -42).asBoolean)
-        assertTrue(RuntimeValueNumeric(DataType.FLOAT, -42.0).asBoolean)
-    }
-
-
-    @Test
-    fun testIdentity() {
-        val v = RuntimeValueNumeric(DataType.UWORD, 12345)
-        assertEquals(v, v)
-        assertFalse(v != v)
-        assertTrue(v<=v)
-        assertTrue(v>=v)
-        assertFalse(v<v)
-        assertFalse(v>v)
-
-        assertTrue(sameValueAndType(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UBYTE, 100)))
-    }
-
-    @Test
-    fun testEqualsAndNotEquals() {
-        assertEquals(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UBYTE, 100))
-        assertEquals(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UWORD, 100))
-        assertEquals(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.FLOAT, 100))
-        assertEquals(RuntimeValueNumeric(DataType.UWORD, 254), RuntimeValueNumeric(DataType.UBYTE, 254))
-        assertEquals(RuntimeValueNumeric(DataType.UWORD, 12345), RuntimeValueNumeric(DataType.UWORD, 12345))
-        assertEquals(RuntimeValueNumeric(DataType.UWORD, 12345), RuntimeValueNumeric(DataType.FLOAT, 12345))
-        assertEquals(RuntimeValueNumeric(DataType.FLOAT, 100.0), RuntimeValueNumeric(DataType.UBYTE, 100))
-        assertEquals(RuntimeValueNumeric(DataType.FLOAT, 22239.0), RuntimeValueNumeric(DataType.UWORD, 22239))
-        assertEquals(RuntimeValueNumeric(DataType.FLOAT, 9.99), RuntimeValueNumeric(DataType.FLOAT, 9.99))
-
-        assertTrue(sameValueAndType(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UBYTE, 100)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UWORD, 100)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.FLOAT, 100)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UWORD, 254), RuntimeValueNumeric(DataType.UBYTE, 254)))
-        assertTrue(sameValueAndType(RuntimeValueNumeric(DataType.UWORD, 12345), RuntimeValueNumeric(DataType.UWORD, 12345)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UWORD, 12345), RuntimeValueNumeric(DataType.FLOAT, 12345)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.FLOAT, 100.0), RuntimeValueNumeric(DataType.UBYTE, 100)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.FLOAT, 22239.0), RuntimeValueNumeric(DataType.UWORD, 22239)))
-        assertTrue(sameValueAndType(RuntimeValueNumeric(DataType.FLOAT, 9.99), RuntimeValueNumeric(DataType.FLOAT, 9.99)))
-
-        assertNotEquals(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UBYTE, 101))
-        assertNotEquals(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UWORD, 101))
-        assertNotEquals(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.FLOAT, 101))
-        assertNotEquals(RuntimeValueNumeric(DataType.UWORD, 245), RuntimeValueNumeric(DataType.UBYTE, 246))
-        assertNotEquals(RuntimeValueNumeric(DataType.UWORD, 12345), RuntimeValueNumeric(DataType.UWORD, 12346))
-        assertNotEquals(RuntimeValueNumeric(DataType.UWORD, 12345), RuntimeValueNumeric(DataType.FLOAT, 12346))
-        assertNotEquals(RuntimeValueNumeric(DataType.FLOAT, 9.99), RuntimeValueNumeric(DataType.UBYTE, 9))
-        assertNotEquals(RuntimeValueNumeric(DataType.FLOAT, 9.99), RuntimeValueNumeric(DataType.UWORD, 9))
-        assertNotEquals(RuntimeValueNumeric(DataType.FLOAT, 9.99), RuntimeValueNumeric(DataType.FLOAT, 9.0))
-
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UBYTE, 101)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.UWORD, 101)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UBYTE, 100), RuntimeValueNumeric(DataType.FLOAT, 101)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UWORD, 245), RuntimeValueNumeric(DataType.UBYTE, 246)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UWORD, 12345), RuntimeValueNumeric(DataType.UWORD, 12346)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.UWORD, 12345), RuntimeValueNumeric(DataType.FLOAT, 12346)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.FLOAT, 9.99), RuntimeValueNumeric(DataType.UBYTE, 9)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.FLOAT, 9.99), RuntimeValueNumeric(DataType.UWORD, 9)))
-        assertFalse(sameValueAndType(RuntimeValueNumeric(DataType.FLOAT, 9.99), RuntimeValueNumeric(DataType.FLOAT, 9.0)))
-    }
-
-    @Test
-    fun testGreaterThan(){
-        assertTrue(RuntimeValueNumeric(DataType.UBYTE, 100) > RuntimeValueNumeric(DataType.UBYTE, 99))
-        assertTrue(RuntimeValueNumeric(DataType.UWORD, 254) > RuntimeValueNumeric(DataType.UWORD, 253))
-        assertTrue(RuntimeValueNumeric(DataType.FLOAT, 100.0) > RuntimeValueNumeric(DataType.FLOAT, 99.9))
-
-        assertTrue(RuntimeValueNumeric(DataType.UBYTE, 100) >= RuntimeValueNumeric(DataType.UBYTE, 100))
-        assertTrue(RuntimeValueNumeric(DataType.UWORD, 254) >= RuntimeValueNumeric(DataType.UWORD, 254))
-        assertTrue(RuntimeValueNumeric(DataType.FLOAT, 100.0) >= RuntimeValueNumeric(DataType.FLOAT, 100.0))
-
-        assertFalse(RuntimeValueNumeric(DataType.UBYTE, 100) > RuntimeValueNumeric(DataType.UBYTE, 100))
-        assertFalse(RuntimeValueNumeric(DataType.UWORD, 254) > RuntimeValueNumeric(DataType.UWORD, 254))
-        assertFalse(RuntimeValueNumeric(DataType.FLOAT, 100.0) > RuntimeValueNumeric(DataType.FLOAT, 100.0))
-
-        assertFalse(RuntimeValueNumeric(DataType.UBYTE, 100) >= RuntimeValueNumeric(DataType.UBYTE, 101))
-        assertFalse(RuntimeValueNumeric(DataType.UWORD, 254) >= RuntimeValueNumeric(DataType.UWORD, 255))
-        assertFalse(RuntimeValueNumeric(DataType.FLOAT, 100.0) >= RuntimeValueNumeric(DataType.FLOAT, 100.1))
-    }
-
-    @Test
-    fun testLessThan() {
-        assertTrue(RuntimeValueNumeric(DataType.UBYTE, 100) < RuntimeValueNumeric(DataType.UBYTE, 101))
-        assertTrue(RuntimeValueNumeric(DataType.UWORD, 254) < RuntimeValueNumeric(DataType.UWORD, 255))
-        assertTrue(RuntimeValueNumeric(DataType.FLOAT, 100.0) < RuntimeValueNumeric(DataType.FLOAT, 100.1))
-
-        assertTrue(RuntimeValueNumeric(DataType.UBYTE, 100) <= RuntimeValueNumeric(DataType.UBYTE, 100))
-        assertTrue(RuntimeValueNumeric(DataType.UWORD, 254) <= RuntimeValueNumeric(DataType.UWORD, 254))
-        assertTrue(RuntimeValueNumeric(DataType.FLOAT, 100.0) <= RuntimeValueNumeric(DataType.FLOAT, 100.0))
-
-        assertFalse(RuntimeValueNumeric(DataType.UBYTE, 100) < RuntimeValueNumeric(DataType.UBYTE, 100))
-        assertFalse(RuntimeValueNumeric(DataType.UWORD, 254) < RuntimeValueNumeric(DataType.UWORD, 254))
-        assertFalse(RuntimeValueNumeric(DataType.FLOAT, 100.0) < RuntimeValueNumeric(DataType.FLOAT, 100.0))
-
-        assertFalse(RuntimeValueNumeric(DataType.UBYTE, 100) <= RuntimeValueNumeric(DataType.UBYTE, 99))
-        assertFalse(RuntimeValueNumeric(DataType.UWORD, 254) <= RuntimeValueNumeric(DataType.UWORD, 253))
-        assertFalse(RuntimeValueNumeric(DataType.FLOAT, 100.0) <= RuntimeValueNumeric(DataType.FLOAT, 99.9))
-    }
-
-    @Test
-    fun testNoDtConversion() {
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UWORD, 100).add(RuntimeValueNumeric(DataType.UBYTE, 120))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UBYTE, 100).add(RuntimeValueNumeric(DataType.UWORD, 120))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.FLOAT, 100.22).add(RuntimeValueNumeric(DataType.UWORD, 120))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UWORD, 1002).add(RuntimeValueNumeric(DataType.FLOAT, 120.22))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.FLOAT, 100.22).add(RuntimeValueNumeric(DataType.UBYTE, 120))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UBYTE, 12).add(RuntimeValueNumeric(DataType.FLOAT, 120.22))
-        }
-    }
-
-    @Test
-    fun testNoAutoFloatConversion() {
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UBYTE, 233).add(RuntimeValueNumeric(DataType.FLOAT, 1.234))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UWORD, 233).add(RuntimeValueNumeric(DataType.FLOAT, 1.234))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UBYTE, 233).mul(RuntimeValueNumeric(DataType.FLOAT, 1.234))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UWORD, 233).mul(RuntimeValueNumeric(DataType.FLOAT, 1.234))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UBYTE, 233).div(RuntimeValueNumeric(DataType.FLOAT, 1.234))
-        }
-        assertFailsWith<ArithmeticException> {
-            RuntimeValueNumeric(DataType.UWORD, 233).div(RuntimeValueNumeric(DataType.FLOAT, 1.234))
-        }
-        val result = RuntimeValueNumeric(DataType.FLOAT, 233.333).add(RuntimeValueNumeric(DataType.FLOAT, 1.234))
-    }
-
-    @Test
-    fun arithmetictestUbyte() {
-        assertEquals(255, RuntimeValueNumeric(DataType.UBYTE, 200).add(RuntimeValueNumeric(DataType.UBYTE, 55)).integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 200).add(RuntimeValueNumeric(DataType.UBYTE, 56)).integerValue())
-        assertEquals(1, RuntimeValueNumeric(DataType.UBYTE, 200).add(RuntimeValueNumeric(DataType.UBYTE, 57)).integerValue())
-
-        assertEquals(1, RuntimeValueNumeric(DataType.UBYTE, 2).sub(RuntimeValueNumeric(DataType.UBYTE, 1)).integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 2).sub(RuntimeValueNumeric(DataType.UBYTE, 2)).integerValue())
-        assertEquals(255, RuntimeValueNumeric(DataType.UBYTE, 2).sub(RuntimeValueNumeric(DataType.UBYTE, 3)).integerValue())
-
-        assertEquals(255, RuntimeValueNumeric(DataType.UBYTE, 254).inc().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 255).inc().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 1).dec().integerValue())
-        assertEquals(255, RuntimeValueNumeric(DataType.UBYTE, 0).dec().integerValue())
-
-        assertEquals(255, RuntimeValueNumeric(DataType.UBYTE, 0).inv().integerValue())
-        assertEquals(0b00110011, RuntimeValueNumeric(DataType.UBYTE, 0b11001100).inv().integerValue())
-//        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 0).neg().integerValue())
-//        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 0).neg().integerValue())
-        assertEquals(1, RuntimeValueNumeric(DataType.UBYTE, 0).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 1).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 111).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UBYTE, 255).not().integerValue())
-
-        assertEquals(200, RuntimeValueNumeric(DataType.UBYTE, 20).mul(RuntimeValueNumeric(DataType.UBYTE, 10)).integerValue())
-        assertEquals(144, RuntimeValueNumeric(DataType.UBYTE, 20).mul(RuntimeValueNumeric(DataType.UBYTE, 20)).integerValue())
-
-        assertEquals(25, RuntimeValueNumeric(DataType.UBYTE, 5).pow(RuntimeValueNumeric(DataType.UBYTE, 2)).integerValue())
-        assertEquals(125, RuntimeValueNumeric(DataType.UBYTE, 5).pow(RuntimeValueNumeric(DataType.UBYTE, 3)).integerValue())
-        assertEquals(113, RuntimeValueNumeric(DataType.UBYTE, 5).pow(RuntimeValueNumeric(DataType.UBYTE, 4)).integerValue())
-
-        assertEquals(100, RuntimeValueNumeric(DataType.UBYTE, 50).shl().integerValue())
-        assertEquals(200, RuntimeValueNumeric(DataType.UBYTE, 100).shl().integerValue())
-        assertEquals(144, RuntimeValueNumeric(DataType.UBYTE, 200).shl().integerValue())
-    }
-
-    @Test
-    fun arithmetictestUWord() {
-        assertEquals(65535, RuntimeValueNumeric(DataType.UWORD, 60000).add(RuntimeValueNumeric(DataType.UWORD, 5535)).integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 60000).add(RuntimeValueNumeric(DataType.UWORD, 5536)).integerValue())
-        assertEquals(1, RuntimeValueNumeric(DataType.UWORD, 60000).add(RuntimeValueNumeric(DataType.UWORD, 5537)).integerValue())
-
-        assertEquals(1, RuntimeValueNumeric(DataType.UWORD, 2).sub(RuntimeValueNumeric(DataType.UWORD, 1)).integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 2).sub(RuntimeValueNumeric(DataType.UWORD, 2)).integerValue())
-        assertEquals(65535, RuntimeValueNumeric(DataType.UWORD, 2).sub(RuntimeValueNumeric(DataType.UWORD, 3)).integerValue())
-
-        assertEquals(65535, RuntimeValueNumeric(DataType.UWORD, 65534).inc().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 65535).inc().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 1).dec().integerValue())
-        assertEquals(65535, RuntimeValueNumeric(DataType.UWORD, 0).dec().integerValue())
-
-        assertEquals(65535, RuntimeValueNumeric(DataType.UWORD, 0).inv().integerValue())
-        assertEquals(0b0011001101010101, RuntimeValueNumeric(DataType.UWORD, 0b1100110010101010).inv().integerValue())
-//        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 0).neg().integerValue())
-//        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 0).neg().integerValue())
-        assertEquals(1, RuntimeValueNumeric(DataType.UWORD, 0).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 1).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 11111).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.UWORD, 65535).not().integerValue())
-
-        assertEquals(2000, RuntimeValueNumeric(DataType.UWORD, 200).mul(RuntimeValueNumeric(DataType.UWORD, 10)).integerValue())
-        assertEquals(40000, RuntimeValueNumeric(DataType.UWORD, 200).mul(RuntimeValueNumeric(DataType.UWORD, 200)).integerValue())
-        assertEquals(14464, RuntimeValueNumeric(DataType.UWORD, 200).mul(RuntimeValueNumeric(DataType.UWORD, 400)).integerValue())
-
-        assertEquals(15625, RuntimeValueNumeric(DataType.UWORD, 5).pow(RuntimeValueNumeric(DataType.UWORD, 6)).integerValue())
-        assertEquals(12589, RuntimeValueNumeric(DataType.UWORD, 5).pow(RuntimeValueNumeric(DataType.UWORD, 7)).integerValue())
-
-        assertEquals(10000, RuntimeValueNumeric(DataType.UWORD, 5000).shl().integerValue())
-        assertEquals(60000, RuntimeValueNumeric(DataType.UWORD, 30000).shl().integerValue())
-        assertEquals(14464, RuntimeValueNumeric(DataType.UWORD, 40000).shl().integerValue())
-    }
-
-    @Test
-    fun arithmetictestByte() {
-        assertEquals(127, RuntimeValueNumeric(DataType.BYTE, 100).add(RuntimeValueNumeric(DataType.BYTE, 27)).integerValue())
-        assertEquals(-128, RuntimeValueNumeric(DataType.BYTE, 100).add(RuntimeValueNumeric(DataType.BYTE, 28)).integerValue())
-        assertEquals(-127, RuntimeValueNumeric(DataType.BYTE, 100).add(RuntimeValueNumeric(DataType.BYTE, 29)).integerValue())
-
-        assertEquals(1, RuntimeValueNumeric(DataType.BYTE, 2).sub(RuntimeValueNumeric(DataType.BYTE, 1)).integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.BYTE, 2).sub(RuntimeValueNumeric(DataType.BYTE, 2)).integerValue())
-        assertEquals(-1, RuntimeValueNumeric(DataType.BYTE, 2).sub(RuntimeValueNumeric(DataType.BYTE, 3)).integerValue())
-        assertEquals(-128, RuntimeValueNumeric(DataType.BYTE, -100).sub(RuntimeValueNumeric(DataType.BYTE, 28)).integerValue())
-        assertEquals(127, RuntimeValueNumeric(DataType.BYTE, -100).sub(RuntimeValueNumeric(DataType.BYTE, 29)).integerValue())
-
-        assertEquals(127, RuntimeValueNumeric(DataType.BYTE, 126).inc().integerValue())
-        assertEquals(-128, RuntimeValueNumeric(DataType.BYTE, 127).inc().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.BYTE, 1).dec().integerValue())
-        assertEquals(-1, RuntimeValueNumeric(DataType.BYTE, 0).dec().integerValue())
-        assertEquals(-128, RuntimeValueNumeric(DataType.BYTE, -127).dec().integerValue())
-        assertEquals(127, RuntimeValueNumeric(DataType.BYTE, -128).dec().integerValue())
-
-        assertEquals(-1, RuntimeValueNumeric(DataType.BYTE, 0).inv().integerValue())
-        assertEquals(-103, RuntimeValueNumeric(DataType.BYTE, 0b01100110).inv().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.BYTE, 0).neg().integerValue())
-        assertEquals(-2, RuntimeValueNumeric(DataType.BYTE, 2).neg().integerValue())
-        assertEquals(1, RuntimeValueNumeric(DataType.BYTE, 0).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.BYTE, 1).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.BYTE, 111).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.BYTE, -33).not().integerValue())
-
-        assertEquals(100, RuntimeValueNumeric(DataType.BYTE, 10).mul(RuntimeValueNumeric(DataType.BYTE, 10)).integerValue())
-        assertEquals(-56, RuntimeValueNumeric(DataType.BYTE, 20).mul(RuntimeValueNumeric(DataType.BYTE, 10)).integerValue())
-
-        assertEquals(25, RuntimeValueNumeric(DataType.BYTE, 5).pow(RuntimeValueNumeric(DataType.BYTE, 2)).integerValue())
-        assertEquals(125, RuntimeValueNumeric(DataType.BYTE, 5).pow(RuntimeValueNumeric(DataType.BYTE, 3)).integerValue())
-        assertEquals(113, RuntimeValueNumeric(DataType.BYTE, 5).pow(RuntimeValueNumeric(DataType.BYTE, 4)).integerValue())
-
-        assertEquals(100, RuntimeValueNumeric(DataType.BYTE, 50).shl().integerValue())
-        assertEquals(-56, RuntimeValueNumeric(DataType.BYTE, 100).shl().integerValue())
-        assertEquals(-2, RuntimeValueNumeric(DataType.BYTE, -1).shl().integerValue())
-    }
-
-    @Test
-    fun arithmetictestWorrd() {
-        assertEquals(32767, RuntimeValueNumeric(DataType.WORD, 32700).add(RuntimeValueNumeric(DataType.WORD, 67)).integerValue())
-        assertEquals(-32768, RuntimeValueNumeric(DataType.WORD, 32700).add(RuntimeValueNumeric(DataType.WORD, 68)).integerValue())
-        assertEquals(-32767, RuntimeValueNumeric(DataType.WORD, 32700).add(RuntimeValueNumeric(DataType.WORD, 69)).integerValue())
-
-        assertEquals(1, RuntimeValueNumeric(DataType.WORD, 2).sub(RuntimeValueNumeric(DataType.WORD, 1)).integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.WORD, 2).sub(RuntimeValueNumeric(DataType.WORD, 2)).integerValue())
-        assertEquals(-1, RuntimeValueNumeric(DataType.WORD, 2).sub(RuntimeValueNumeric(DataType.WORD, 3)).integerValue())
-        assertEquals(-32768, RuntimeValueNumeric(DataType.WORD, -32700).sub(RuntimeValueNumeric(DataType.WORD, 68)).integerValue())
-        assertEquals(32767, RuntimeValueNumeric(DataType.WORD, -32700).sub(RuntimeValueNumeric(DataType.WORD, 69)).integerValue())
-
-        assertEquals(32767, RuntimeValueNumeric(DataType.WORD, 32766).inc().integerValue())
-        assertEquals(-32768, RuntimeValueNumeric(DataType.WORD, 32767).inc().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.WORD, 1).dec().integerValue())
-        assertEquals(-1, RuntimeValueNumeric(DataType.WORD, 0).dec().integerValue())
-        assertEquals(-32768, RuntimeValueNumeric(DataType.WORD, -32767).dec().integerValue())
-        assertEquals(32767, RuntimeValueNumeric(DataType.WORD, -32768).dec().integerValue())
-
-        assertEquals(-1, RuntimeValueNumeric(DataType.WORD, 0).inv().integerValue())
-        assertEquals(-103, RuntimeValueNumeric(DataType.WORD, 0b01100110).inv().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.WORD, 0).neg().integerValue())
-        assertEquals(-2, RuntimeValueNumeric(DataType.WORD, 2).neg().integerValue())
-        assertEquals(1, RuntimeValueNumeric(DataType.WORD, 0).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.WORD, 1).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.WORD, 111).not().integerValue())
-        assertEquals(0, RuntimeValueNumeric(DataType.WORD, -33).not().integerValue())
-
-        assertEquals(10000, RuntimeValueNumeric(DataType.WORD, 100).mul(RuntimeValueNumeric(DataType.WORD, 100)).integerValue())
-        assertEquals(-25536, RuntimeValueNumeric(DataType.WORD, 200).mul(RuntimeValueNumeric(DataType.WORD, 200)).integerValue())
-
-        assertEquals(15625, RuntimeValueNumeric(DataType.WORD, 5).pow(RuntimeValueNumeric(DataType.WORD, 6)).integerValue())
-        assertEquals(-6487, RuntimeValueNumeric(DataType.WORD, 9).pow(RuntimeValueNumeric(DataType.WORD, 5)).integerValue())
-
-        assertEquals(18000, RuntimeValueNumeric(DataType.WORD, 9000).shl().integerValue())
-        assertEquals(-25536, RuntimeValueNumeric(DataType.WORD, 20000).shl().integerValue())
-        assertEquals(-2, RuntimeValueNumeric(DataType.WORD, -1).shl().integerValue())
-    }
-}
@@ -16,7 +16,6 @@ import prog8.compiler.target.c64.C64MachineDefinition.FLOAT_MAX_NEGATIVE
 import prog8.compiler.target.c64.C64MachineDefinition.FLOAT_MAX_POSITIVE
 import prog8.compiler.target.c64.C64MachineDefinition.Mflpt5
 import prog8.compiler.target.c64.Petscii
-import prog8.vm.RuntimeValueNumeric
 import java.io.CharConversionException
 import kotlin.test.*

@@ -124,7 +123,7 @@ class TestCompiler {


@TestInstance(TestInstance.Lifecycle.PER_CLASS)
-class TestZeropage {
+class TestC64Zeropage {

    private val errors = ErrorReporter()

@@ -186,7 +185,7 @@ class TestZeropage {
        val zp1 = C64Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.BASICSAFE, emptyList(), true))
        assertEquals(16, zp1.available())
        val zp2 = C64Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.FLOATSAFE, emptyList(), false))
-        assertEquals(91, zp2.available())
+        assertEquals(89, zp2.available())
        val zp3 = C64Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.KERNALSAFE, emptyList(), false))
        assertEquals(125, zp3.available())
        val zp4 = C64Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.FULL, emptyList(), false))
@@ -356,8 +355,8 @@ class TestPetscii {

    @Test
    fun testLiteralValueComparisons() {
-        val ten = NumericLiteralValue(DataType.UWORD, 10, Position("", 0, 0, 0))
-        val nine = NumericLiteralValue(DataType.UBYTE, 9, Position("", 0, 0, 0))
+        val ten = NumericLiteralValue(DataType.UWORD, 10, Position.DUMMY)
+        val nine = NumericLiteralValue(DataType.UBYTE, 9, Position.DUMMY)
        assertEquals(ten, ten)
        assertNotEquals(ten, nine)
        assertFalse(ten != ten)
@@ -373,30 +372,10 @@ class TestPetscii {
        assertTrue(ten <= ten)
        assertFalse(ten < ten)

-        val abc = StringLiteralValue("abc", false, Position("", 0, 0, 0))
-        val abd = StringLiteralValue("abd", false, Position("", 0, 0, 0))
+        val abc = StringLiteralValue("abc", false, Position.DUMMY)
+        val abd = StringLiteralValue("abd", false, Position.DUMMY)
        assertEquals(abc, abc)
        assertTrue(abc!=abd)
        assertFalse(abc!=abc)
    }
-
-    @Test
-    fun testStackvmValueComparisons() {
-        val ten = RuntimeValueNumeric(DataType.FLOAT, 10)
-        val nine = RuntimeValueNumeric(DataType.UWORD, 9)
-        assertEquals(ten, ten)
-        assertNotEquals(ten, nine)
-        assertFalse(ten != ten)
-        assertTrue(ten != nine)
-
-        assertTrue(ten > nine)
-        assertTrue(ten >= nine)
-        assertTrue(ten >= ten)
-        assertFalse(ten > ten)
-
-        assertFalse(ten < nine)
-        assertFalse(ten <= nine)
-        assertTrue(ten <= ten)
-        assertFalse(ten < ten)
-    }
 }
@@ -83,7 +83,7 @@ For normal use the compiler is invoked with the command:
 By default, assembly code is generated and written to ``sourcefile.asm``.
 It is then (automatically) fed to the `64tass <https://sourceforge.net/projects/tass64/>`_ cross assembler tool
 that assembles it into the final program.
-If you use the option to let the compiler auto-start a C-64 emulator, it will do so after
+If you use the option to let the compiler auto-start an emulator, it will do so after
 a successful compilation. This will load your program and the symbol and breakpoint lists
 (for the machine code monitor) into the emulator.

@@ -109,8 +109,8 @@ A module source file is a text file with the ``.p8`` suffix, containing the prog
 It consists of compilation options and other directives, imports of other modules,
 and source code for one or more code blocks.

-Prog8 has a couple of *LIBRARY* modules that are defined in special internal files provided by the compiler:
-``c64lib``, ``c64utils``, ``c64flt`` and ``prog8lib``. You should not overwrite these or reuse their names.
+Prog8 has various *LIBRARY* modules that are defined in special internal files provided by the compiler.
+You should not overwrite these or reuse their names.
 They are embedded into the packaged release version of the compiler so you don't have to worry about
 where they are, but their names are still reserved.

@@ -149,10 +149,10 @@ If your running program hits one of the breakpoints, Vice will halt execution an
 Troubleshooting
 ---------------

-Getting an assembler error about undefined symbols such as ``not defined 'c64flt'``?
-This happens when your program uses floating point values, and you forgot to import ``c64flt`` library.
+Getting an assembler error about undefined symbols such as ``not defined 'floats'``?
+This happens when your program uses floating point values, and you forgot to import ``floats`` library.
 If you use floating points, the compiler needs routines from that library.
-Fix it by adding an ``%import c64flt``.
+Fix it by adding an ``%import floats``.


 Examples
@@ -168,18 +168,3 @@ or::

    $ ./p8compile.sh -emu examples/rasterbars.p8

-
-
-Virtual Machine / Simulator
---------------------------
-
-You may have noticed the ``-sim`` command line option for the compiler:
-
-sim
-    Launches the "AST virtual machine Simulator" that directly executes the parsed program.
-    No compilation steps will be performed.
-    Allows for very fast testing and debugging before actually compiling programs
-    to machine code.
-    It simulates a bare minimum of features from the target platform, so most stuff
-    that calls ROM routines or writes into hardware registers won't work. But basic
-    system routines are emulated.
@@ -12,6 +12,7 @@ What is Prog8?

 This is an experimental compiled programming language targeting the 8-bit
 `6502 <https://en.wikipedia.org/wiki/MOS_Technology_6502>`_ /
+`65c02 <https://en.wikipedia.org/wiki/MOS_Technology_65C02>`_ /
 `6510 <https://en.wikipedia.org/wiki/MOS_Technology_6510>`_ microprocessor.
 This CPU is from the late 1970's and early 1980's and was used in many home computers from that era,
 such as the `Commodore-64 <https://en.wikipedia.org/wiki/Commodore_64>`_.
@@ -37,49 +38,49 @@ This software is licensed under the GNU GPL 3.0, see https://www.gnu.org/license
    :alt: Fully playable tetris clone


-Code examples
-------------
+Code example
+------------

 This code calculates prime numbers using the Sieve of Eratosthenes algorithm::

-    %import c64utils
+    %import textio
    %zeropage basicsafe

    main {
-
        ubyte[256] sieve
-        ubyte candidate_prime = 2
+        ubyte candidate_prime = 2       ; is increased in the loop

        sub start() {
+            ; clear the sieve, to reset starting situation on subsequent runs
            memset(sieve, 256, false)
-
-            c64scr.print("prime numbers up to 255:\n\n")
+            ; calculate primes
+            txt.print("prime numbers up to 255:\n\n")
            ubyte amount=0
-            while true {
+            repeat {
                ubyte prime = find_next_prime()
                if prime==0
                    break
-                c64scr.print_ub(prime)
-                c64scr.print(", ")
+                txt.print_ub(prime)
+                txt.print(", ")
                amount++
            }
-            c64.CHROUT('\n')
-            c64scr.print("number of primes (expected 54): ")
-            c64scr.print_ub(amount)
-            c64.CHROUT('\n')
+            txt.chrout('\n')
+            txt.print("number of primes (expected 54): ")
+            txt.print_ub(amount)
+            txt.chrout('\n')
        }

-
        sub find_next_prime() -> ubyte {
-
            while sieve[candidate_prime] {
                candidate_prime++
                if candidate_prime==0
-                    return 0
+                    return 0        ; we wrapped; no more primes available in the sieve
            }

+            ; found next one, mark the multiples and return it.
            sieve[candidate_prime] = true
            uword multiple = candidate_prime
+
            while multiple < len(sieve) {
                sieve[lsb(multiple)] = true
                multiple += candidate_prime
@@ -96,70 +97,36 @@ when compiled an ran on a C-64 you get this:
    :alt: result when run on C-64


-The following programs shows a use of the high level ``struct`` type::
-
-    %import c64utils
-    %zeropage basicsafe
-
-    main {
-
-        struct Color {
-            ubyte red
-            ubyte green
-            ubyte blue
-        }
-
-        sub start() {
-
-            Color purple = {255, 0, 255}
-            Color other
-            other = purple
-            other.red /= 2
-            other.green = 10 + other.green / 2
-            other.blue = 99
-
-            c64scr.print_ub(other.red)
-            c64.CHROUT(',')
-            c64scr.print_ub(other.green)
-            c64.CHROUT(',')
-            c64scr.print_ub(other.blue)
-            c64.CHROUT('\n')
-        }
-    }
-
-when compiled and ran, it prints  ``127,10,99`` on the screen.
-

 Design principles and features
 ------------------------------

 - It is a cross-compiler running on modern machines (Linux, MacOS, Windows, ...)
  The generated output is a machine code program runnable on actual 8-bit 6502 hardware.
- Usable on most operating systems.
- Based on simple and familiar imperative structured programming paradigm.
- 'One statement per line' code style, resulting in clear readable programs.
+- Based on simple and familiar imperative structured programming (it looks like a mix of C and Python)
+- 'One statement per line' code, resulting in clear readable programs.
 - Modular programming and scoping via modules, code blocks, and subroutines.
- Provide high level programming constructs but stay close to the metal;
-  still able to directly use memory addresses, CPU registers and ROM subroutines,
-  and inline assembly to have full control when every cycle or byte matters
- Arbitrary number of subroutine parameters (constrained only by available memory)
- Nested subroutines can access variables from outer scopes, this avoids the need and overhead to pass everything via parameters
+- Provide high level programming constructs but at the same time stay close to the metal;
+  still able to directly use memory addresses and ROM subroutines,
+  and inline assembly to have full control when every register, cycle or byte matters
+- Arbitrary number of subroutine parameters
 - Complex nested expressions are possible
- Values are typed. Types supported include signed and unsigned bytes and words, arrays, strings and floats.
+- Nested subroutines can access variables from outer scopes to avoids the overhead to pass everything via parameters
+- Values are typed. Available data types include signed and unsigned bytes and words, arrays, strings and floats.
 - No dynamic memory allocation or sizing! All variables stay fixed size as determined at compile time.
 - Provide various quality of life language features and library subroutines specifically for the target platform.
 - Provide a very convenient edit/compile/run cycle by being able to directly launch
-  the compiled program in an emulator and provide debugging information to the emulator.
- The compiler outputs a regular 6502 assembly source code file, but doesn't assemble this itself.
-  The (separate) '64tass' cross-assembler tool is used for that.
+  the compiled program in an emulator and provide debugging information to this emulator.
 - Arbitrary control flow jumps and branches are possible,
  and will usually translate directly into the appropriate single 6502 jump/branch instruction.
 - There are no complicated built-in error handling or overflow checks, you'll have to take care
  of this yourself if required. This keeps the language and code simple and efficient.
- The compiler tries to optimize the program and generated code, but hand-tuning of the
+- The compiler tries to optimize the program and generated code a bit, but hand-tuning of the
  performance or space-critical parts will likely still be required. This is supported by
  the ability to easily write embedded assembly code directly in the program source code.
- There are many built-in functions, such as ``sin``, ``cos``, ``rnd``, ``abs``, ``min``, ``max``, ``sqrt``, ``msb``, ``rol``, ``ror``, ``swap``, ``memset``, ``memcopy``, ``sort`` and ``reverse``
+- There are many built-in functions, such as ``sin``, ``cos``, ``rnd``, ``abs``, ``min``, ``max``, ``sqrt``, ``msb``, ``rol``, ``ror``, ``swap``, ``memset``, ``memcopy``, ``substr``, ``sort`` and ``reverse`` (and others)
+- Assembling the generated code into a program wil be done by an external cross-assembler tool.
+- If you only use standard kernel and prog8 library routines, it is possible to compile the *exact same program* for both machines (just change the compiler target flag)!


 .. _requirements:
@@ -177,6 +144,7 @@ Fnd for Windows it's possible to get that as well. Check out `AdoptOpenJDK <http

 Finally: a **C-64 emulator** (or a real C-64 ofcourse) can be nice to test and run your programs on.
 The compiler assumes the presence of the `Vice emulator <http://vice-emu.sourceforge.net/>`_.
+If you're targeting the CommanderX16, there's the `x16emu <https://github.com/commanderx16/x16-emulator>`_.

 .. important::
    **Building the compiler itself:** (*Only needed if you have not downloaded a pre-built 'fat-jar'*)
@@ -50,7 +50,7 @@ Code
    There are different kinds of instructions ('statements' is a better name) such as:

    - value assignment
-    - looping  (for, while, repeat, unconditional jumps)
+    - looping  (for, while, do-until, repeat, unconditional jumps)
    - conditional execution (if - then - else, when, and conditional jumps)
    - subroutine calls
    - label definition
@@ -135,14 +135,18 @@ Scopes are created using either of these two statements:
 - blocks  (top-level named scope)
 - subroutines   (nested named scope)

-.. note::
-    Unlike many other programming languages, a new scope is *not* created inside
-    for, while and repeat statements, nor for the if statement and branching conditionals.
-    This can be a bit restrictive because as a programmer you have to think harder about what variables you
-    want to use inside a subroutine. But it is done precisely for this reason: memory in prog8's
+.. important::
+    Unlike most other programming languages, a new scope is *not* created inside
+    for, while, repeat, and do-until statements, the if statement, and the branching conditionals.
+    These all share the same scope from the subroutine they're defined in.
+    You can define variables in these blocks, but these will be treated as if they
+    were defined in the subroutine instead.
+    This can seem a bit restrictive because you have to think harder about what variables you
+    want to use inside the subroutine, to avoid clashes.
+    But this decision was made for a good reason: memory in prog8's
    target systems is usually very limited and it would be a waste to allocate a lot of variables.
    The prog8 compiler is not yet advanced enough to be able to share or overlap
-    variables intelligently. So for now that is something the programmer has to think about.
+    variables intelligently. So for now that is something you have to think about yourself.


 Program Start and Entry Point
@@ -152,13 +156,6 @@ Your program must have a single entry point where code execution begins.
 The compiler expects a ``start`` subroutine in the ``main`` block for this,
 taking no parameters and having no return value.

-.. sidebar::
-    60hz IRQ entry point
-
-    When running the generated code on the StackVm virtual machine,
-    it will use the ``irq`` subroutine in the ``irq`` block for the
-    60hz irq routine. This is optional.
-
 As any subroutine, it has to end with a ``return`` statement (or a ``goto`` call)::

    main {
@@ -181,7 +178,7 @@ Variables and values
 --------------------

 Variables are named values that can change during the execution of the program.
-They can be defined inside any scope (blocks, subroutines, for loops, etc.) See :ref:`Scopes <scopes>`.
+They can be defined inside any scope (blocks, subroutines etc.) See :ref:`Scopes <scopes>`.
 When declaring a numeric variable it is possible to specify the initial value, if you don't want it to be zero.
 For other data types it is required to specify that initial value it should get.
 Values will usually be part of an expression or assignment statement::
@@ -207,13 +204,6 @@ Example::
    byte  @zp  zeropageCounter = 42


-Variables that represent CPU hardware registers
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-The following variables are reserved
-and map directly (read/write) to a CPU hardware register: ``A``, ``X``, ``Y``.
-
-
 Integers
 ^^^^^^^^

@@ -236,7 +226,7 @@ This is because routines in the C-64 BASIC and KERNAL ROMs are used for that.
 So floating point operations will only work if the C-64 BASIC ROM (and KERNAL ROM)
 are banked in.

-Also your code needs to import the ``c64flt`` library to enable floating point support
+Also your code needs to import the ``floats`` library to enable floating point support
 in the compiler, and to gain access to the floating point routines.
 (this library contains the directive to enable floating points, you don't have
 to worry about this yourself)
@@ -267,6 +257,16 @@ Note that the various keywords for the data type and variable type (``byte``, ``
 can't be used as *identifiers* elsewhere. You can't make a variable, block or subroutine with the name ``byte``
 for instance.

+**Arrays at a specific memory location:**
+Using the memory-mapped syntax it is possible to define an array to be located at a specific memory location.
+For instance to reference the first 5 rows of the Commodore 64's screen matrix as an array, you can define::
+
+    &ubyte[5*40]  top5screenrows = $0400
+
+This way you can set the second character on the second row from the top like this::
+
+    top5screenrows[41] = '!'
+

 Strings
 ^^^^^^^
@@ -282,16 +282,23 @@ This @-prefix can also be used for character byte values.


 You can concatenate two string literals using '+' (not very useful though) or repeat
-a string literal a given number of times using '*'::
+a string literal a given number of times using '*'. You can also assign a new string
+value to another string. No bounds check is done so be sure the destination string is
+large enough to contain the new value::

    str string1 = "first part" + "second part"
    str string2 = "hello!" * 10

+    string1 = string2
+    string1 = "new value"
+

 .. caution::
-    Avoid changing strings after they've been created.
+    It's probably best to avoid changing strings after they've been created. This
+    includes changing certain letters by index, or by assigning a new value, or by
+    modifying the string via other means for example ``substr`` function and its cousins.
    This is because if your program exits and is restarted (without loading it again),
-    it will then start working with the changed strings instead of the original ones.
+    it will then start working with the changed strings instead of the original ones!
    The same is true for arrays.


@@ -375,10 +382,8 @@ Initial values across multiple runs of the program

 When declaring values with an initial value, this value will be set into the variable each time
 the program reaches the declaration again. This can be in loops, multiple subroutine calls,
-or even multiple invocations of the entire program.  If you omit an initial value, it will
-be set to zero *but only for the first run of the program*. A second run will utilize the last value
-where it left off (but your code will be a bit smaller because no initialization instructions
-are generated)
+or even multiple invocations of the entire program.
+If you omit the initial value, zero will be used instead.

 This only works for simple types, *and not for string variables and arrays*.
 It is assumed these are left unchanged by the program; they are not re-initialized on
@@ -387,34 +392,25 @@ If you do modify them in-place, you should take care yourself that they work as
 expected when the program is restarted.
 (This is an optimization choice to avoid having to store two copies of every string and array)

-.. caution::
-   variables that get allocated in zero-page will *not* have a zero starting value when you omit
-   the variable's initialization. They'll be whatever the last value in that zero page
-   location was. So it's best to don't depend on the uninitialized starting value!
-
-.. warning::
-    this behavior may change in a future version so that subsequent runs always
-    use the same initial values
-

 Loops
 -----

-The *for*-loop is used to let a variable (or register) iterate over a range of values. Iteration is done in steps of 1, but you can change this.
+The *for*-loop is used to let a variable iterate over a range of values. Iteration is done in steps of 1, but you can change this.
 The loop variable must be declared as byte or word earlier so you can reuse it for multiple occasions.
 Iterating with a floating point variable is not supported. If you want to loop over a floating-point array, use a loop with an integer index variable instead.

 The *while*-loop is used to repeat a piece of code while a certain condition is still true.
-The *repeat--until* loop is used to repeat a piece of code until a certain condition is true.
-
-The *forever*-loop is used to simply run a piece of code in a loop, forever. You can still
-break out of this loop if desired. A "while true" or "until false" loop is equivalent to
-a forever-loop.
+The *do--until* loop is used to repeat a piece of code until a certain condition is true.
+The *repeat* loop is used as a short notation of a for loop where the loop variable doesn't matter and you're only interested in the number of iterations.
+(without iteration count specified it simply loops forever).

 You can also create loops by using the ``goto`` statement, but this should usually be avoided.

+Breaking out of a loop prematurely is possible with the ``break`` statement.
+
 .. attention::
-    The value of the loop variable or register after executing the loop *is undefined*. Don't use it immediately
+    The value of the loop variable after executing the loop *is undefined*. Don't use it immediately
    after the loop without first assigning a new value to it!
    (this is an optimization issue to avoid having to deal with mostly useless post-loop logic to adjust the loop variable's value)

@@ -428,15 +424,15 @@ if statements
 Conditional execution means that the flow of execution changes based on certiain conditions,
 rather than having fixed gotos or subroutine calls::

-	if A>4 goto overflow
+	if aa>4 goto overflow

-	if X==3  Y = 4
-	if X==3  Y = 4 else  A = 2
+	if xx==3  yy = 4
+	if xx==3  yy = 4 else  aa = 2

-	if X==5 {
-		Y = 99
+	if xx==5 {
+		yy = 99
 	} else {
-		A = 3
+		aa = 3
 	}


@@ -500,16 +496,16 @@ Assignments
 -----------

 Assignment statements assign a single value to a target variable or memory location.
-Augmented assignments (such as ``A += X``) are also available, but these are just shorthands
-for normal assignments (``A = A + X``).
+Augmented assignments (such as ``aa += xx``) are also available, but these are just shorthands
+for normal assignments (``aa = aa + xx``).

-Only register variables and variables of type byte, word and float can be assigned a new value.
+Only variables of type byte, word and float can be assigned a new value.
 It's not possible to set a new value to string or array variables etc, because they get allocated
-a fixed amount of memory which will not change.
+a fixed amount of memory which will not change.  (You *can* change the value of elements in a string or array though).

 .. attention::
    **Data type conversion (in assignments):**
-    When assigning a value with a 'smaller' datatype to a register or variable with a 'larger' datatype,
+    When assigning a value with a 'smaller' datatype to variable with a 'larger' datatype,
    the value will be automatically converted to the target datatype:  byte --> word --> float.
    So assigning a byte to a word variable, or a word to a floating point variable, is fine.
    The reverse is *not* true: it is *not* possible to assign a value of a 'larger' datatype to
@@ -525,7 +521,7 @@ as the memory mapped address $d021.
 If you want to access a memory location directly (by using the address itself), without defining
 a memory mapped location, you can do so by enclosing the address in ``@(...)``::

-    A = @($d020)      ; set the A register to the current c64 screen border color ("peek(53280)")
+    color = @($d020)  ; set the variable 'color' to the current c64 screen border color ("peek(53280)")
    @($d020) = 0      ; set the c64 screen border to black ("poke 53280,0")
    @(vic+$20) = 6    ; you can also use expressions to 'calculate' the address

@@ -582,25 +578,24 @@ within parentheses will be evaluated first. So ``(4 + 8) * 2`` is 24 and not 20,
 and ``(true or false) and false`` is false instead of true.

 .. attention::
-    **calculations keep their datatype:**
+    **calculations keep their datatype even if the target variable is larger:**
    When you do calculations on a BYTE type, the result will remain a BYTE.
    When you do calculations on a WORD type, the result will remain a WORD.
    For instance::

        byte b = 44
        word w = b*55   ; the result will be 116! (even though the target variable is a word)
-        w *= 999        ; the result will be -15188  (the multiplication stays within a word)
+        w *= 999        ; the result will be -15188  (the multiplication stays within a word, but overflows)

-    The compiler will NOT give a warning about this! It's doing this for
+    *The compiler does NOT warn about this!* It's doing this for
    performance reasons - so you won't get sudden 16 bit (or even float)
    calculations where you needed only simple fast byte arithmetic.
    If you do need the extended resulting value, cast at least one of the
-    operands of an operator to the larger datatype. For example::
+    operands explicitly to the larger datatype. For example::

        byte b = 44
-        word w = b*55.w     ; the result will be 2420
-        w = (b as word)*55  ; same result
-
+        w = (b as word)*55
+        w = b*(55 as word)



@@ -728,11 +723,17 @@ reverse(array)

 len(x)
    Number of values in the array value x, or the number of characters in a string (excluding the size or 0-byte).
-    Note: this can be different from the number of *bytes* in memory if the datatype isn't a byte.
+    Note: this can be different from the number of *bytes* in memory if the datatype isn't a byte. See sizeof().
    Note: lengths of strings and arrays are determined at compile-time! If your program modifies the actual
    length of the string during execution, the value of len(string) may no longer be correct!
    (use strlen function if you want to dynamically determine the length)

+sizeof(name)
+    Number of bytes that the object 'name' occupies in memory. This is a constant determined by the data type of
+    the object. For instance, for a variable of type uword, the sizeof is 2.
+    For an 10 element array of floats, it is 50 (on the C-64, where a float is 5 bytes).
+    Note: usually you will be interested in the number of elements in an array, use len() for that.
+
 strlen(str)
    Number of bytes in the string. This value is determined during runtime and counts upto
    the first terminating 0 byte in the string, regardless of the size of the string during compilation time.
@@ -746,8 +747,9 @@ msb(x)
 sgn(x)
    Get the sign of the value. Result is -1, 0 or 1 (negative, zero, positive).

-mkword(lsb, msb)
-    Efficiently create a word value from two bytes (the lsb and the msb). Avoids multiplication and shifting.
+mkword(msb, lsb)
+    Efficiently create a word value from two bytes (the msb and the lsb). Avoids multiplication and shifting.
+    So mkword($80, $22) results in $8022.

 any(x)
    1 ('true') if any of the values in the array value x is 'true' (not zero), else 0 ('false')
@@ -764,16 +766,6 @@ rndw()
 rndf()
    returns a pseudo-random float between 0.0 and 1.0

-lsl(x)
-    Shift the bits in x (byte or word) one position to the left.
-    Bit 0 is set to 0 (and the highest bit is shifted into the status register's Carry flag)
-    Modifies in-place, doesn't return a value (so can't be used in an expression).
-
-lsr(x)
-    Shift the bits in x (byte or word) one position to the right.
-    The highest bit is set to 0 (and bit 0 is shifted into the status register's Carry flag)
-    Modifies in-place, doesn't return a value (so can't be used in an expression).
-
 rol(x)
    Rotate the bits in x (byte or word) one position to the left.
    This uses the CPU's rotate semantics: bit 0 will be set to the current value of the Carry flag,
@@ -810,12 +802,28 @@ memset(address, numbytes, bytevalue)
    Efficiently set a part of memory to the given (u)byte value.
    But the most efficient will always be to write a specialized fill routine in assembly yourself!
    Note that for clearing the character screen, very fast specialized subroutines are
-    available in the ``c64scr`` block (part of the ``c64utils`` module)
+    available in the ``txt`` block (part of the ``textio`` module)

 memsetw(address, numwords, wordvalue)
    Efficiently set a part of memory to the given (u)word value.
    But the most efficient will always be to write a specialized fill routine in assembly yourself!

+leftstr(source, target, length)
+    Copies the left side of the source string of the given length to target string.
+    It is assumed the target string buffer is large enough to contain the result.
+    Modifies in-place, doesn't return a value (so can't be used in an expression).
+
+rightstr(source, target, length)
+    Copies the right side of the source string of the given length to target string.
+    It is assumed the target string buffer is large enough to contain the result.
+    Modifies in-place, doesn't return a value (so can't be used in an expression).
+
+substr(source, target, start, length)
+    Copies a segment from the source string, starting at the given index,
+    and of the given length to target string.
+    It is assumed the target string buffer is large enough to contain the result.
+    Modifies in-place, doesn't return a value (so can't be used in an expression).
+
 swap(x, y)
    Swap the values of numerical variables (or memory locations) x and y in a fast way.

@@ -24,7 +24,7 @@ Everything after a semicolon ``;`` is a comment and is ignored.
 If the whole line is just a comment, it will be copied into the resulting assembly source code.
 This makes it easier to understand and relate the generated code. Examples::

-	A = 42    ; set the initial value to 42
+	counter = 42    ; set the initial value to 42
 	; next is the code that...


@@ -33,6 +33,13 @@ This makes it easier to understand and relate the generated code. Examples::
 Directives
 -----------

+.. data:: %target <target>
+
+    Level: module.
+    Global setting, specifies that this module can only work for the given compiler target.
+    If compiled with a different target, compilation is aborted with an error message.
+
+
 .. data:: %output <type>

 	Level: module.
@@ -157,7 +164,7 @@ Directives
 Identifiers
 -----------

-Naming things in Prog8 is done via valid *identifiers*. They start with a letter or underscore,
+Naming things in Prog8 is done via valid *identifiers*. They start with a letter,
 and after that, a combination of letters, numbers, or underscores. Examples of valid identifiers::

 	a
@@ -165,7 +172,7 @@ and after that, a combination of letters, numbers, or underscores. Examples of v
 	monkey
 	COUNTER
 	Better_Name_2
-	_something_strange_
+	something_strange__


 Code blocks
@@ -216,7 +223,8 @@ Variable declarations

 Variables should be declared with their exact type and size so the compiler can allocate storage
 for them. You can give them an initial value as well. That value can be a simple literal value,
-or an expression. You can add a ``@zp`` zeropage-tag, to tell the compiler to prioritize it
+or an expression. If you don't provide an intial value yourself, zero will be used.
+You can add a ``@zp`` zeropage-tag, to tell the compiler to prioritize it
 when selecting variables to be put into zeropage.
 The syntax is::

@@ -288,7 +296,8 @@ of something with an operand starting with 1 or 0, you'll have to add a space in
 - When an integer value ranges from 256..65535 the compiler sees it as a ``uword``.  For -32768..32767 it's a ``word``.
 - When a hex number has 3 or 4 digits, for example ``$0004``, it is seen as a ``word`` otherwise as a ``byte``.
 - When a binary number has 9 to 16 digits, for example ``%1100110011``, it is seen as a ``word`` otherwise as a ``byte``.
- You can force a byte value into a word value by adding the ``.w`` datatype suffix to the number: ``$2a.w`` is equivalent to ``$002a``.
+- If the number fits in a byte but you really require it as a word value, you'll have to explicitly cast it: ``60 as uword``
+  or you can use the full word hexadecimal notation ``$003c``.


 Data type conversion
@@ -305,6 +314,7 @@ should be allocated by the compiler. Instead, the (mandatory) value assigned to
 should be the *memory address* where the value is located::

 	&byte BORDERCOLOR = $d020
+    &ubyte[5*40]  top5screenrows = $0400        ; works for array as well


 Direct access to memory locations
@@ -312,7 +322,7 @@ Direct access to memory locations
 Instead of defining a memory mapped name for a specific memory location, you can also
 directly access the memory. Enclose a numeric expression or literal with ``@(...)`` to do that::

-    A = @($d020)      ; set the A register to the current c64 screen border color ("peek(53280)")
+    color = @($d020)  ; set the variable 'color' to the current c64 screen border color ("peek(53280)")
    @($d020) = 0      ; set the c64 screen border to black ("poke 53280,0")
    @(vic+$20) = 6    ; a dynamic expression to 'calculate' the address

@@ -321,7 +331,7 @@ Constants
 ^^^^^^^^^

 All variables can be assigned new values unless you use the ``const`` keyword.
-The initial value will now be evaluated at compile time (it must be a compile time constant expression).
+The initial value must be known at compile time (it must be a compile time constant expression).
 This is only valid for the simple numeric types (byte, word, float)::

 	const  byte  max_age = 99
@@ -332,8 +342,6 @@ Reserved names

 The following names are reserved, they have a special meaning::

-	A     X    Y              ; 6502 hardware registers
-	Pc    Pz   Pn  Pv         ; 6502 status register flags
 	true  false              ; boolean values 1 and 0


@@ -405,10 +413,10 @@ assignment: ``=``
    Note that an assignment sometimes is not possible or supported.

 augmented assignment: ``+=``  ``-=``  ``*=``  ``/=``  ``**=``  ``&=``  ``|=``  ``^=``  ``<<=``  ``>>=``
-	Syntactic sugar; ``A += X`` is equivalent to ``A = A + X``
+	This is syntactic sugar; ``aa += xx`` is equivalent to ``aa = aa + xx``

 postfix increment and decrement: ``++``  ``--``
-	Syntactic sugar; ``A++`` is equivalent to ``A = A + 1``, and ``A--`` is equivalent to ``A = A - 1``.
+	Syntactic sugar; ``aa++`` is equivalent to ``aa = aa + 1``, and ``aa--`` is equivalent to ``aa = aa - 1``.
 	Because these operations are so common, we have these short forms.

 comparison: ``!=``  ``<``  ``>``  ``<=``  ``>=``
@@ -426,9 +434,9 @@ range creation:  ``to``

 		0 to 7		; range of values 0, 1, 2, 3, 4, 5, 6, 7  (constant)

-		A = 5
-		X = 10
-		A to X		; range of 5, 6, 7, 8, 9, 10
+		aa = 5
+		aa = 10
+	    aa to xx		; range of 5, 6, 7, 8, 9, 10

 		byte[] array = 10 to 13   ; sets the array to [1, 2, 3, 4]

@@ -514,18 +522,20 @@ and returning stuff in several registers as well. The ``clobbers`` clause is use
 what CPU registers are clobbered by the call instead of being unchanged or returning a meaningful result value.


-Subroutines that are implemented purely in assembly code and which have an assembly calling convention (i.e.
-the parameters are strictly passed via cpu registers), are defined like this::
+User subroutines in the program source code that are implemented purely in assembly and which have an assembly calling convention (i.e.
+the parameters are strictly passed via cpu registers), are defined with ``asmsub`` like this::

-    asmsub  FREADS32() clobbers(A,X,Y)  {
+    asmsub  clear_screenchars (ubyte char @ A) clobbers(Y)  {
        %asm {{
-            lda  $62
-            eor  #$ff
-            asl  a
-            lda  #0
-            ldx  #$a0
-            jmp  $bc4f
-        }}
+            ldy  #0
+    _loop   sta  c64.Screen,y
+            sta  c64.Screen+$0100,y
+            sta  c64.Screen+$0200,y
+            sta  c64.Screen+$02e8,y
+            iny
+            bne  _loop
+            rts
+            }}
    }

 the statement body of such a subroutine should consist of just an inline assembly block.
@@ -550,7 +560,7 @@ Loops
 for loop
 ^^^^^^^^

-The loop variable must be a register or a byte/word variable,
+The loop variable must be a byte or word variable,
 and must be defined first in the local scope of the for loop.
 The expression that you loop over can be anything that supports iteration (such as ranges like ``0 to 100``,
 array variables and strings) *except* floating-point arrays (because a floating-point loop variable is not supported).
@@ -560,7 +570,6 @@ You can use a single statement, or a statement block like in the example below::
 	for <loopvar>  in  <expression>  [ step <amount> ]   {
 		; do something...
 		break		; break out of the loop
-		continue	; immediately enter next iteration
 	}

 For example, this is a for loop using a byte variable ``i``, defined before, to loop over a certain range of numbers::
@@ -593,35 +602,35 @@ You can use a single statement, or a statement block like in the example below::
 	while  <condition>  {
 		; do something...
 		break		; break out of the loop
-		continue	; immediately enter next iteration
 	}


-repeat-until loop
-^^^^^^^^^^^^^^^^^
+do-until loop
+^^^^^^^^^^^^^

 Until the given condition is true (1), repeat the given statement(s).
 You can use a single statement, or a statement block like in the example below::

-	repeat  {
+	do  {
 		; do something...
 		break		; break out of the loop
-		continue	; immediately enter next iteration
 	} until  <condition>


-forever loop
-^^^^^^^^^^^^
+repeat loop
+^^^^^^^^^^^

-Simply run the code in a loop, forever. It's the same as a while true or until false loop,
-or just a jump back to a previous label. You can still break out of this loop as well, if you want::
+When you're only interested in repeating something a given number of times.
+It's a short hand for a for loop without an explicit loop variable::

-    forever {
-        ; .. do stuff
-        if something
-            break        ; you can exit the loop if you want
+    repeat 15 {
+        ; do something...
+        break		; you can break out of the loop
    }

+If you omit the iteration count, it simply loops forever.
+You can still ``break`` out of such a loop if you want though.
+

 Conditional Execution and Jumps
 -------------------------------
@@ -701,3 +710,4 @@ case you have to use { } to enclose them::
        }
        else -> c64scr.print("don't know")
    }
+
@@ -4,12 +4,20 @@ Target system specification

 Prog8 targets the following hardware:

- 8 bit MOS 6502/6510 CPU
+- 8 bit MOS 6502/65c02/6510 CPU
 - 64 Kb addressable memory (RAM or ROM)
- memory mapped I/O registers
+- optional use of memory mapped I/O registers
+- optional use of system ROM routines

-The main target machine is the Commodore-64, which is an example of this.
-This chapter explains the relevant system details of such a machine.
+Currently there are two machines that are supported as compiler target (selectable via the ``-target`` compiler argument):
+
+- 'c64': the well-known Commodore-64, premium support
+- 'cx16': the `CommanderX16 <https://www.commanderx16.com/>`_ a project from the 8-Bit Guy. Support for this is still experimental.
+
+This chapter explains the relevant system details of these machines.
+
+.. note::
+    If you only use standard kernel and prog8 library routines, it is possible to compile the *exact same program* for both machines (just change the compiler target flag)!


 Memory Model
@@ -113,22 +121,14 @@ CPU
 Directly Usable Registers
 -------------------------

-The following 6502 CPU hardware registers are directly usable in program code (and are reserved symbols):
+The hardware CPU registers are not directly accessible from regular Prog8 code.
+If you need to mess with them, you'll have to use inline assembly.
+Be extra wary of the ``X`` register because it is used as an evaluation stack pointer and
+changing its value you will destroy the evaluation stack and likely crash the program.

- ``A``, ``X``, ``Y``  the three main cpu registers (8 bits)
- the status register (P) carry flag and interrupt disable flag can be written via a couple of special
-  builtin functions (``set_carry()``, ``clear_carry()``, ``set_irqd()``,  ``clear_irqd()``),
-  and read via the ``read_flags()`` function.
-
-However, you must assume that the 3 hardware registers ``A``, ``X`` and ``Y``
-are volatile. Their values cannot be depended upon, the compiler will use them as required.
-Even simple assignments may require modification of one or more of the registers (for instance, when using arrays).
-
-Even more important, the ``X`` register is used as an evaluation stack pointer.
-If you mess with it, you will destroy the evaluation stack and likely crash your program.
-In some cases the compiler will warn you about this, but you should really avoid to use
-this register. It's possible to store/restore the register's value (using special built in functions)
-for the cases you really really need to use it directly.
+The status register (P) carry flag and interrupt disable flag can be written via a couple of special
+builtin functions (``set_carry()``, ``clear_carry()``, ``set_irqd()``,  ``clear_irqd()``),
+and read via the ``read_flags()`` function.


 Subroutine Calling Conventions
@@ -155,15 +155,15 @@ You can however install your own IRQ handler.
 This is possible ofcourse by doing it all using customized inline assembly,
 but there are a few library routines available to make setting up C-64 IRQs and raster IRQs a lot easier (no assembly code required).

-These routines are::
+For the C64 these routines are::

-    c64utils.set_irqvec()
-    c64utils.set_irqvec_excl()
+    c64.set_irqvec()
+    c64.set_irqvec_excl()

-    c64utils.set_rasterirq( <raster line> )
-    c64utils.set_rasterirq_excl( <raster line> )
+    c64.set_rasterirq( <raster line> )
+    c64.set_rasterirq_excl( <raster line> )

-    c64utils.restore_irqvec()     ; set it back to the systems default irq handler
+    c64.restore_irqvec()     ; set it back to the systems default irq handler

 If you activate an IRQ handler with one of these, it expects the handler to be defined
 as a subroutine ``irq`` in the module ``irq`` so like this::
@@ -173,3 +173,4 @@ as a subroutine ``irq`` in the module ``irq`` so like this::
            ; ... irq handling here ...
        }
    }
+
@@ -2,42 +2,35 @@
 TODO
 ====

- remove statements after an exit() or return
- fix warnings about that unreachable code?
-
- option to load library files from a directory instead of the embedded ones
-
-
-Memory Block Operations integrated in language?
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-array/string memory block operations?
-
- vector inc/dec/add/sub/mul/div...?  (on array or string):
-  ``arrayvar++ / arrayvar-- / arrayvar += 2 / arrayvar -= 2 / arrayvar *= 3 / arrayvar /= 3``
-
- array operations
-  copy (from another array with the same length), shift-N(left,right), rotate-N(left,right)
-  clear (set whole array to the given value, default 0)
-
- array operations ofcourse work identical on vars and on memory mapped vars of these types.
-
- strings: identical operations as on array.
-
-For now, we have the ``memcopy`` and ``memset`` builtin functions.
-
+- get rid of all other TODO's in the code ;-)
+- move the 	ldx  #$ff | clc | cld  from the startup logic into the start() function as first instructions
+- add an %option that omits the 'system-init' code at the start. Useful to create separate standalone routines that shouldn't re-init the whole machine every time they're called
+- line-circle-gfx examples are now a few hundred bytes larger than before. Why is that, can it be fixed?
+- until condition should be able to refer to variables defined IN the do-until block itself.
+- add support? example? for processing arguments to a sys call : sys 999, 1, 2, "aaa"
+- make it possible for array literals to not only contain compile time constants
+- further optimize assignment codegeneration
+- implement @stack for asmsub parameters
+- make it possible to use cpu opcodes such as 'nop' as variable names by prefixing all asm vars with something such as '_'
+- option to load the built-in library files from a directory instead of the embedded ones (for easier library development/debugging)
+- see if we can group some errors together for instance the (now single) errors about unidentified symbols
+- use VIC banking to move up the graphics bitmap memory location. Don't move it under the ROM though as that would require IRQ disabling and memory bank swapping for every bitmap manipulation
+- add some primitives/support/examples for using custom char sets, copying the default charset.

 More optimizations
 ^^^^^^^^^^^^^^^^^^

 Add more compiler optimizations to the existing ones.

- on the language AST level
- on the final assembly source level
- can the parameter passing to subroutines be optimized to avoid copying?
- working subroutine inlining (taking care of vars and identifier refs to them)
-
-Also some library routines and code patterns could perhaps be optimized further
+- more targeted optimizations for assigment asm code, such as the following:
+- subroutine calling convention? like: 1 byte arg -> pass in A, 2 bytes -> pass in A+Y, return value likewise.
+- can such parameter passing to subroutines be optimized to avoid copying?
+- add a compiler option to not include variable initialization code (useful if the program is expected to run only once, such as a game)
+  the program will then rely solely on the values as they are in memory at the time of program startup.
+- Also some library routines and code patterns could perhaps be optimized further
+- more optimizations on the language AST level
+- more optimizations on the final assembly source level
+- note: subroutine inlining is abandoned because of problems referencing non-local stuff. Can't move everything around.


 Eval stack redesign? (lot of work)
@@ -45,17 +38,18 @@ Eval stack redesign? (lot of work)

 The eval stack is now a split lsb/msb stack using X as the stackpointer.
 Is it easier/faster to just use a single page unsplit stack?
-It could then even be moved into the zeropage to greatly reduce code size and slowness.
+It could then even be moved into the zeropage to reduce code size and slowness.

 Or just move the LSB portion into a slab of the zeropage.

-Allocate a fixed word in ZP that is the TOS so we can always operate on TOS directly
-without having to to index into the stack?
+Allocate a fixed word in ZP that is the Top Of Stack value so we can always operate on TOS directly
+without having to index with X into the eval stack all the time?
+This could GREATLY improve code size and speed for operations that work on just a single value.


-Bugs
-^^^^
-Ofcourse there are still bugs to fix ;)
+Bug Fixing
+^^^^^^^^^^
+Ofcourse there are always bugs to fix ;)


 Misc
@@ -63,4 +57,3 @@ Misc

 Several ideas were discussed on my reddit post
 https://www.reddit.com/r/programming/comments/alhj59/creating_a_programming_language_and_cross/
-
@@ -1,7 +1,6 @@
-%import c64lib
-%import c64utils
-%import c64flt
-%zeropage dontuse
+%import floats
+%import textio
+%zeropage basicsafe

 main {

@@ -20,102 +19,90 @@ main {

        ; LEN/STRLEN
        ubyte length = len(name)
-        if length!=5 c64scr.print("error len1\n")
+        if length!=5 txt.print("error len1\n")
        length = len(uwarr)
-        if length!=5 c64scr.print("error len2\n")
+        if length!=5 txt.print("error len2\n")
        length=strlen(name)
-        if length!=5 c64scr.print("error strlen1\n")
+        if length!=5 txt.print("error strlen1\n")
        name[3] = 0
        length=strlen(name)
-        if length!=3 c64scr.print("error strlen2\n")
+        if length!=3 txt.print("error strlen2\n")

        ; MAX
        ub = max(ubarr)
-        if ub!=199 c64scr.print("error max1\n")
+        if ub!=199 txt.print("error max1\n")
        bb = max(barr)
-        if bb!=99 c64scr.print("error max2\n")
+        if bb!=99 txt.print("error max2\n")
        uw = max(uwarr)
-        if uw!=4444 c64scr.print("error max3\n")
+        if uw!=4444 txt.print("error max3\n")
        ww = max(warr)
-        if ww!=999 c64scr.print("error max4\n")
+        if ww!=999 txt.print("error max4\n")
        ff = max(farr)
-        if ff!=999.9 c64scr.print("error max5\n")
+        if ff!=999.9 txt.print("error max5\n")

        ; MIN
        ub = min(ubarr)
-        if ub!=0 c64scr.print("error min1\n")
+        if ub!=0 txt.print("error min1\n")
        bb = min(barr)
-        if bb!=-122 c64scr.print("error min2\n")
+        if bb!=-122 txt.print("error min2\n")
        uw = min(uwarr)
-        if uw!=0 c64scr.print("error min3\n")
+        if uw!=0 txt.print("error min3\n")
        ww = min(warr)
-        if ww!=-4444 c64scr.print("error min4\n")
+        if ww!=-4444 txt.print("error min4\n")
        ff = min(farr)
-        if ff!=-4444.4 c64scr.print("error min5\n")
+        if ff!=-4444.4 txt.print("error min5\n")

        ; SUM
        uw = sum(ubarr)
-        if uw!=420 c64scr.print("error sum1\n")
+        if uw!=420 txt.print("error sum1\n")
        ww = sum(barr)
-        if ww!=-101 c64scr.print("error sum2\n")
+        if ww!=-101 txt.print("error sum2\n")
        uw = sum(uwarr)
-        if uw!=6665 c64scr.print("error sum3\n")
+        if uw!=6665 txt.print("error sum3\n")
        ww = sum(warr)
-        if ww!=-4223 c64scr.print("error sum4\n")
+        if ww!=-4223 txt.print("error sum4\n")
        ff = sum(farr)
-        if ff!=-4222.4 c64scr.print("error sum5\n")
+        if ff!=-4222.4 txt.print("error sum5\n")

        ; ANY
        ub = any(ubarr)
-        if ub==0 c64scr.print("error any1\n")
+        if ub==0 txt.print("error any1\n")
        ub = any(barr)
-        if ub==0 c64scr.print("error any2\n")
+        if ub==0 txt.print("error any2\n")
        ub = any(uwarr)
-        if ub==0 c64scr.print("error any3\n")
+        if ub==0 txt.print("error any3\n")
        ub = any(warr)
-        if ub==0 c64scr.print("error any4\n")
+        if ub==0 txt.print("error any4\n")
        ub = any(farr)
-        if ub==0 c64scr.print("error any5\n")
+        if ub==0 txt.print("error any5\n")

        ; ALL
        ub = all(ubarr)
-        if ub==1 c64scr.print("error all1\n")
+        if ub==1 txt.print("error all1\n")
        ub = all(barr)
-        if ub==1 c64scr.print("error all2\n")
+        if ub==1 txt.print("error all2\n")
        ub = all(uwarr)
-        if ub==1 c64scr.print("error all3\n")
+        if ub==1 txt.print("error all3\n")
        ub = all(warr)
-        if ub==1 c64scr.print("error all4\n")
+        if ub==1 txt.print("error all4\n")
        ub = all(farr)
-        if ub==1 c64scr.print("error all5\n")
+        if ub==1 txt.print("error all5\n")
        ubarr[1]=$40
        barr[1]=$40
        uwarr[1]=$4000
        warr[1]=$4000
        farr[1]=1.1
        ub = all(ubarr)
-        if ub==0 c64scr.print("error all6\n")
+        if ub==0 txt.print("error all6\n")
        ub = all(barr)
-        if ub==0 c64scr.print("error all7\n")
+        if ub==0 txt.print("error all7\n")
        ub = all(uwarr)
-        if ub==0 c64scr.print("error all8\n")
+        if ub==0 txt.print("error all8\n")
        ub = all(warr)
-        if ub==0 c64scr.print("error all9\n")
+        if ub==0 txt.print("error all9\n")
        ub = all(farr)
-        if ub==0 c64scr.print("error all10\n")
+        if ub==0 txt.print("error all10\n")

-        check_eval_stack()
-
-        c64scr.print("\nyou should see no errors above.")
+        txt.print("\nyou should see no errors printed above (only at first run).")
    }
-
-    sub check_eval_stack() {
-        c64scr.print("x=")
-        c64scr.print_ub(X)
-        if X==255
-            c64scr.print(" ok\n")
-        else
-            c64scr.print(" error!\n")
-    }
-
 }
@@ -1,6 +1,5 @@
-%import c64lib
-%import c64utils
-%import c64flt
+%import floats
+%import textio
 %zeropage basicsafe

 main {
@@ -24,91 +23,81 @@ main {

        div_float(0,1,0)
        div_float(999.9,111.0,9.008108108108107)
-
-        check_eval_stack()
    }

    sub div_ubyte(ubyte a1, ubyte a2, ubyte c) {
        ubyte r = a1/a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("ubyte ")
-        c64scr.print_ub(a1)
-        c64scr.print(" / ")
-        c64scr.print_ub(a2)
-        c64scr.print(" = ")
-        c64scr.print_ub(r)
+            txt.print("err! ")
+        txt.print("ubyte ")
+        txt.print_ub(a1)
+        txt.print(" / ")
+        txt.print_ub(a2)
+        txt.print(" = ")
+        txt.print_ub(r)
        c64.CHROUT('\n')
    }

    sub div_byte(byte a1, byte a2, byte c) {
        byte r = a1/a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("byte ")
-        c64scr.print_b(a1)
-        c64scr.print(" / ")
-        c64scr.print_b(a2)
-        c64scr.print(" = ")
-        c64scr.print_b(r)
+            txt.print("err! ")
+        txt.print("byte ")
+        txt.print_b(a1)
+        txt.print(" / ")
+        txt.print_b(a2)
+        txt.print(" = ")
+        txt.print_b(r)
        c64.CHROUT('\n')
    }

    sub div_uword(uword a1, uword  a2, uword c) {
        uword  r = a1/a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("uword ")
-        c64scr.print_uw(a1)
-        c64scr.print(" / ")
-        c64scr.print_uw(a2)
-        c64scr.print(" = ")
-        c64scr.print_uw(r)
+            txt.print("err! ")
+        txt.print("uword ")
+        txt.print_uw(a1)
+        txt.print(" / ")
+        txt.print_uw(a2)
+        txt.print(" = ")
+        txt.print_uw(r)
        c64.CHROUT('\n')
    }

    sub div_word(word a1, word a2, word c) {
        word r = a1/a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("word ")
-        c64scr.print_w(a1)
-        c64scr.print(" / ")
-        c64scr.print_w(a2)
-        c64scr.print(" = ")
-        c64scr.print_w(r)
+            txt.print("err! ")
+        txt.print("word ")
+        txt.print_w(a1)
+        txt.print(" / ")
+        txt.print_w(a2)
+        txt.print(" = ")
+        txt.print_w(r)
        c64.CHROUT('\n')
    }

    sub div_float(float  a1, float a2, float  c) {
        float r = a1/a2
        if abs(r-c)<0.00001
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
+            txt.print("err! ")

-        c64scr.print("float ")
-        c64flt.print_f(a1)
-        c64scr.print(" / ")
-        c64flt.print_f(a2)
-        c64scr.print(" = ")
-        c64flt.print_f(r)
+        txt.print("float ")
+        floats.print_f(a1)
+        txt.print(" / ")
+        floats.print_f(a2)
+        txt.print(" = ")
+        floats.print_f(r)
        c64.CHROUT('\n')
    }
-
-    sub check_eval_stack() {
-        if X!=255 {
-            c64scr.print("x=")
-            c64scr.print_ub(X)
-            c64scr.print(" error!\n")
-        }
-    }
 }
@@ -1,6 +1,5 @@
-%import c64lib
-%import c64utils
-%import c64flt
+%import floats
+%import textio
 %zeropage basicsafe

 main {
@@ -32,92 +31,81 @@ main {
        minus_float(0,0,0)
        minus_float(2.5,1.5,1.0)
        minus_float(-1.5,3.5,-5.0)
-
-        check_eval_stack()
    }

    sub minus_ubyte(ubyte a1, ubyte a2, ubyte c) {
        ubyte r = a1-a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("ubyte ")
-        c64scr.print_ub(a1)
-        c64scr.print(" - ")
-        c64scr.print_ub(a2)
-        c64scr.print(" = ")
-        c64scr.print_ub(r)
+            txt.print("err! ")
+        txt.print("ubyte ")
+        txt.print_ub(a1)
+        txt.print(" - ")
+        txt.print_ub(a2)
+        txt.print(" = ")
+        txt.print_ub(r)
        c64.CHROUT('\n')
    }

    sub minus_byte(byte a1, byte a2, byte c) {
        byte r = a1-a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("byte ")
-        c64scr.print_b(a1)
-        c64scr.print(" - ")
-        c64scr.print_b(a2)
-        c64scr.print(" = ")
-        c64scr.print_b(r)
+            txt.print("err! ")
+        txt.print("byte ")
+        txt.print_b(a1)
+        txt.print(" - ")
+        txt.print_b(a2)
+        txt.print(" = ")
+        txt.print_b(r)
        c64.CHROUT('\n')
    }

    sub minus_uword(uword a1, uword  a2, uword c) {
        uword  r = a1-a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("uword ")
-        c64scr.print_uw(a1)
-        c64scr.print(" - ")
-        c64scr.print_uw(a2)
-        c64scr.print(" = ")
-        c64scr.print_uw(r)
+            txt.print("err! ")
+        txt.print("uword ")
+        txt.print_uw(a1)
+        txt.print(" - ")
+        txt.print_uw(a2)
+        txt.print(" = ")
+        txt.print_uw(r)
        c64.CHROUT('\n')
    }

    sub minus_word(word a1, word a2, word c) {
        word r = a1-a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("word ")
-        c64scr.print_w(a1)
-        c64scr.print(" - ")
-        c64scr.print_w(a2)
-        c64scr.print(" = ")
-        c64scr.print_w(r)
+            txt.print("err! ")
+        txt.print("word ")
+        txt.print_w(a1)
+        txt.print(" - ")
+        txt.print_w(a2)
+        txt.print(" = ")
+        txt.print_w(r)
        c64.CHROUT('\n')
    }

    sub minus_float(float  a1, float a2, float  c) {
        float r = a1-a2
        if abs(r-c)<0.00001
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
+            txt.print("err! ")

-        c64scr.print("float ")
-        c64flt.print_f(a1)
-        c64scr.print(" - ")
-        c64flt.print_f(a2)
-        c64scr.print(" = ")
-        c64flt.print_f(r)
+        txt.print("float ")
+        floats.print_f(a1)
+        txt.print(" - ")
+        floats.print_f(a2)
+        txt.print(" = ")
+        floats.print_f(r)
        c64.CHROUT('\n')
    }
-
-    sub check_eval_stack() {
-        if X!=255 {
-            c64scr.print("x=")
-            c64scr.print_ub(X)
-            c64scr.print(" error!\n")
-        }
-    }
-
 }
@@ -1,6 +1,5 @@
-%import c64lib
-%import c64utils
-%import c64flt
+%import floats
+%import textio
 %zeropage basicsafe

 main {
@@ -26,91 +25,81 @@ main {
        mul_float(0,0,0)
        mul_float(2.5,10,25)
        mul_float(-1.5,10,-15)
-
-        check_eval_stack()
    }

    sub mul_ubyte(ubyte a1, ubyte a2, ubyte c) {
        ubyte r = a1*a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("ubyte ")
-        c64scr.print_ub(a1)
-        c64scr.print(" * ")
-        c64scr.print_ub(a2)
-        c64scr.print(" = ")
-        c64scr.print_ub(r)
+            txt.print("err! ")
+        txt.print("ubyte ")
+        txt.print_ub(a1)
+        txt.print(" * ")
+        txt.print_ub(a2)
+        txt.print(" = ")
+        txt.print_ub(r)
        c64.CHROUT('\n')
    }

    sub mul_byte(byte a1, byte a2, byte c) {
        byte r = a1*a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("byte ")
-        c64scr.print_b(a1)
-        c64scr.print(" * ")
-        c64scr.print_b(a2)
-        c64scr.print(" = ")
-        c64scr.print_b(r)
+            txt.print("err! ")
+        txt.print("byte ")
+        txt.print_b(a1)
+        txt.print(" * ")
+        txt.print_b(a2)
+        txt.print(" = ")
+        txt.print_b(r)
        c64.CHROUT('\n')
    }

    sub mul_uword(uword a1, uword  a2, uword c) {
        uword  r = a1*a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("uword ")
-        c64scr.print_uw(a1)
-        c64scr.print(" * ")
-        c64scr.print_uw(a2)
-        c64scr.print(" = ")
-        c64scr.print_uw(r)
+            txt.print("err! ")
+        txt.print("uword ")
+        txt.print_uw(a1)
+        txt.print(" * ")
+        txt.print_uw(a2)
+        txt.print(" = ")
+        txt.print_uw(r)
        c64.CHROUT('\n')
    }

    sub mul_word(word a1, word a2, word c) {
        word r = a1*a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("word ")
-        c64scr.print_w(a1)
-        c64scr.print(" * ")
-        c64scr.print_w(a2)
-        c64scr.print(" = ")
-        c64scr.print_w(r)
+            txt.print("err! ")
+        txt.print("word ")
+        txt.print_w(a1)
+        txt.print(" * ")
+        txt.print_w(a2)
+        txt.print(" = ")
+        txt.print_w(r)
        c64.CHROUT('\n')
    }

    sub mul_float(float  a1, float a2, float  c) {
        float r = a1*a2
        if abs(r-c)<0.00001
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
+            txt.print("err! ")

-        c64scr.print("float ")
-        c64flt.print_f(a1)
-        c64scr.print(" * ")
-        c64flt.print_f(a2)
-        c64scr.print(" = ")
-        c64flt.print_f(r)
+        txt.print("float ")
+        floats.print_f(a1)
+        txt.print(" * ")
+        floats.print_f(a2)
+        txt.print(" = ")
+        floats.print_f(r)
        c64.CHROUT('\n')
    }
-
-    sub check_eval_stack() {
-        if X!=255 {
-            c64scr.print("x=")
-            c64scr.print_ub(X)
-            c64scr.print(" error!\n")
-        }
-    }
 }
@@ -1,6 +1,5 @@
-%import c64lib
-%import c64utils
-%import c64flt
+%import floats
+%import textio
 %zeropage basicsafe

 main {
@@ -30,92 +29,81 @@ main {
        plus_float(1.5,2.5,4.0)
        plus_float(-1.5,3.5,2.0)
        plus_float(-1.1,3.3,2.2)
-
-        check_eval_stack()
    }

    sub plus_ubyte(ubyte a1, ubyte a2, ubyte c) {
        ubyte r = a1+a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("ubyte ")
-        c64scr.print_ub(a1)
-        c64scr.print(" + ")
-        c64scr.print_ub(a2)
-        c64scr.print(" = ")
-        c64scr.print_ub(r)
+            txt.print("err! ")
+        txt.print("ubyte ")
+        txt.print_ub(a1)
+        txt.print(" + ")
+        txt.print_ub(a2)
+        txt.print(" = ")
+        txt.print_ub(r)
        c64.CHROUT('\n')
    }

    sub plus_byte(byte a1, byte a2, byte c) {
        byte r = a1+a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("byte ")
-        c64scr.print_b(a1)
-        c64scr.print(" + ")
-        c64scr.print_b(a2)
-        c64scr.print(" = ")
-        c64scr.print_b(r)
+            txt.print("err! ")
+        txt.print("byte ")
+        txt.print_b(a1)
+        txt.print(" + ")
+        txt.print_b(a2)
+        txt.print(" = ")
+        txt.print_b(r)
        c64.CHROUT('\n')
    }

    sub plus_uword(uword a1, uword  a2, uword c) {
        uword  r = a1+a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("uword ")
-        c64scr.print_uw(a1)
-        c64scr.print(" + ")
-        c64scr.print_uw(a2)
-        c64scr.print(" = ")
-        c64scr.print_uw(r)
+            txt.print("err! ")
+        txt.print("uword ")
+        txt.print_uw(a1)
+        txt.print(" + ")
+        txt.print_uw(a2)
+        txt.print(" = ")
+        txt.print_uw(r)
        c64.CHROUT('\n')
    }

    sub plus_word(word a1, word a2, word c) {
        word r = a1+a2
        if r==c
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
-        c64scr.print("word ")
-        c64scr.print_w(a1)
-        c64scr.print(" + ")
-        c64scr.print_w(a2)
-        c64scr.print(" = ")
-        c64scr.print_w(r)
+            txt.print("err! ")
+        txt.print("word ")
+        txt.print_w(a1)
+        txt.print(" + ")
+        txt.print_w(a2)
+        txt.print(" = ")
+        txt.print_w(r)
        c64.CHROUT('\n')
    }

    sub plus_float(float  a1, float a2, float  c) {
        float r = a1+a2
        if abs(r-c)<0.00001
-            c64scr.print(" ok  ")
+            txt.print(" ok  ")
        else
-            c64scr.print("err! ")
+            txt.print("err! ")

-        c64scr.print("float ")
-        c64flt.print_f(a1)
-        c64scr.print(" + ")
-        c64flt.print_f(a2)
-        c64scr.print(" = ")
-        c64flt.print_f(r)
+        txt.print("float ")
+        floats.print_f(a1)
+        txt.print(" + ")
+        floats.print_f(a2)
+        txt.print(" = ")
+        floats.print_f(r)
        c64.CHROUT('\n')
    }
-
-    sub check_eval_stack() {
-        if X!=255 {
-            c64scr.print("x=")
-            c64scr.print_ub(X)
-            c64scr.print(" error!\n")
-        }
-    }
-
 }
@@ -1 +1 @@
 .81
 .3