Speedy Gonzales update 5

added syntax checking & runtime error messages

readme.txt

@@ -70,3 +70,106 @@
      density with interpreter performance, while
      remaining within the 1KB constraint.  Structured
      programming principles remained at low priority.
+
+-----------------------------------------------------
+ VTL02sg for the 2m5 emulated 6502 SBC
+
+   spaces in expressions are allowed on input but are 
+     removed from the stored program and listing.
+
+   added a timer variable {/} with 10ms increments.
+
+   the {?} input variable no longer accepts an
+     expression as input. Only a number is accepted. 
+
+   added braces as shift operators.
+     A}B shifts A by B bits to the right.
+     A{B shifts A by B bits to the left.
+     result is unpredictable if B > 16
+
+   an expression missing the initial {=} operator
+     is converted by duplicating the leftmost variable
+     and inserting a {=}. {N+1} becomes {N=N+1}.
+
+   added a statement delimiter {;} allowing multi
+     statement lines.
+     branch to same line is now allowed.
+     {?="..."} & unmatched {)} (used for comments) can
+     not be continued. 
+
+   added load and save facility to user call {>}
+     "=0;>=13  loads program 13 from EEPROM
+     "=1;>=42  saves current program to EEPROM as 42
+     requires emulator version >= 0.83c 
+
+   line numbers >= 65280 are now reserved for the
+     following fast return & goto features.
+   added a gosub stack, depth = 16 address words.
+     {==...} is a gosub and pushes the return address
+     of the next line.
+     {#==} is a return and pops the address when the
+     result is the special line numer asigned to {=}.
+   added a 31 line addresses acronym label array.
+     lowercase characters and symbols in the $60-$7e
+     range are used to address the array. the array
+     is populated with the address of a line when a
+     character in the allowed range preceeds the line
+     number.
+
+   example (prints the first 1000 prime numbers):
+       10 /=0;Q=d;V=5;U=25;X=1000
+       20 N=2;==b
+       30 N+1;==b
+       40 N+2;==b
+      a100 N+2;==b
+       120 N+4;==b
+       150 #=a
+      b200 #=N<U[Q;Q=c;V+2;U=V*V
+      c300 D=5
+      e310 A=N/D;#=%]=;D+2;#=D>V[d
+       320 A=N/D;#=%]=;D+4;#=D<V[e
+      d400 ?=N;?=""
+       420 X=X-1;#=X[=
+       435 ?="Execution time: ";
+       445 ?=//100;$=46;#=%>10[465;?=0
+       465 ?=%;?=" seconds"
+
+   added message service including error messages
+     runtime errors:
+       233 EEPROM file corrupted
+       234 EEPROM file has incompatible format
+       237 EEPROM not responding
+       238 EEPROM full - file not saved
+       239 EEPROM file not found
+       240 array pointer exceeds reserved VTL RAM
+       241 user call pointer inside reserved VTL RAM
+       248 duplicate label
+       249 undefined label or empty return stack
+     errors during program line input:
+       242 invalid or missing operator
+       243 invalid or missing target variable 
+       244 value or variable missing after operator
+       245 missing closing parenthesis
+       246 out of memory (*-&)
+
+ internal changes:
+   added required atomic variable fetch & store.
+   replaced some jsr calls with inline code
+     for skpbyte:, getbyte:, plus:, minus:.
+   replaced cvbin calls to mul: & plus: with custom
+     inline multiply by 10 & digit adder.
+   removed simulation from startup of eval:.
+   mainloop uses inline code to advance to next
+     sequential program line.
+     find: is now only used for true branches.
+   added decimal to binary conversion on line entry
+     avoiding the runtime conversion.
+   abbreviated getting a simple variable in getval:.
+   bypassed setting a simple variable in exec:.
+   added inline divide by 10 to prnum:.
+   fixed statement delimiter not overriding mismatched
+     parentheses.
+   merged oper: into getval: and progr: into exec:
+   added a check for ctrl-c & ctrl-z during goto to
+     allow user escape from a loop.
+