proper error message for arrays that are declared too big

compiler/src/prog8/ast/processing/AstChecker.kt

@@ -492,8 +492,7 @@ internal class AstChecker(private val program: Program,
 
                 when(decl.value) {
                     null -> {
-                        // a vardecl without an initial value, don't bother with the rest
-                        return super.visit(decl)
+                        // 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 -> {
@@ -577,6 +576,26 @@ internal class AstChecker(private val program: Program,
             }
         }
 
+        // array length limits
+        if(decl.isArray) {
+            val length = decl.arraysize!!.size() ?: 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)
     }
 

compiler/src/prog8/compiler/target/c64/codegen/ForLoopsAsmGen.kt

@@ -266,7 +266,6 @@ $endLabel       inx""")
     }
 
     private fun translateForOverIterableVar(stmt: ForLoop, iterableDt: DataType, ident: IdentifierReference) {
-        // TODO optimize this more
         val loopLabel = asmgen.makeLabel("for_loop")
         val endLabel = asmgen.makeLabel("for_end")
         asmgen.loopEndLabels.push(endLabel)
@@ -291,9 +290,9 @@ $loopLabel          lda  ${65535.toHex()}       ; modified
 $endLabel""")
             }
             DataType.ARRAY_UB, DataType.ARRAY_B -> {
-                // TODO: optimize loop code when the length of the array is < 256   (i.e. always)
+                // TODO: optimize loop code when the length of the array is 255 or less instead of 256
                 val length = decl.arraysize!!.size()!!
-                val counterLabel = asmgen.makeLabel("for_counter")      // todo allocate dynamically, zero page preferred if iterations >= 8
+                val counterLabel = asmgen.makeLabel("for_counter")      // todo allocate dynamically, zero page preferred if len >= 16
                 val modifiedLabel = asmgen.makeLabel("for_modified")
                 asmgen.out("""
                     lda  #<$iterableName
@@ -315,9 +314,9 @@ $counterLabel       .byte  0
 $endLabel""")
             }
             DataType.ARRAY_W, DataType.ARRAY_UW -> {
-                // TODO: optimize loop code when the length of the array is < 256  (i.e. always)
+                // TODO: optimize loop code when the length of the array is 255 or less instead of 256
                 val length = decl.arraysize!!.size()!! * 2
-                val counterLabel = asmgen.makeLabel("for_counter")    // todo allocate dynamically, zero page preferred if iterations >= 8
+                val counterLabel = asmgen.makeLabel("for_counter")    // todo allocate dynamically, zero page preferred if len >= 16
                 val modifiedLabel = asmgen.makeLabel("for_modified")
                 val modifiedLabel2 = asmgen.makeLabel("for_modified2")
                 val loopvarName = asmgen.asmIdentifierName(stmt.loopVar)

compiler/src/prog8/functions/BuiltinFunctions.kt

@@ -274,22 +274,16 @@ private fun builtinLen(args: List<Expression>, position: Position, program: Prog
             arraySize = target.arraysize?.size()
             if(arraySize==null)
                 throw CannotEvaluateException("len", "arraysize unknown")
-            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==null)
                 throw CannotEvaluateException("len", "arraysize unknown")
-            if(arraySize>256)
-                throw CompilerException("array length exceeds byte limit ${target.position}")
             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)

docs/source/programming.rst

@@ -257,6 +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
 ^^^^^^^

docs/source/syntaxreference.rst

@@ -306,6 +306,7 @@ 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

docs/source/todo.rst

@@ -2,8 +2,8 @@
 TODO
 ====
 
+- optimize assignment codegeneration
 - get rid of all TODO's ;-)
-- allow declaring arrays on specific memory location and page-aligned
 - option to load the built-in library files from a directory instead of the embedded ones (for easier library development/debugging)
 - aliases for imported symbols for example perhaps '%alias print = c64scr.print' ?
 - investigate support for 8bitguy's Commander X16 platform https://www.commanderx16.com  and https://github.com/commanderx16/x16-docs

examples/test.p8

@@ -24,20 +24,20 @@ main {
 ;        c64.CHROUT('\n')
 
 
-;        ubyte bb
-;        ubyte from = 10
-;        ubyte end = 20
-;
-;        for bb in from to end step 3 {
-;            c64scr.print_ub(bb)
-;            c64.CHROUT(',')
-;        }
-;        c64.CHROUT('\n')
-;        for bb in end to from step -3 {
-;            c64scr.print_ub(bb)
-;            c64.CHROUT(',')
-;        }
-;        c64.CHROUT('\n')
+        ubyte bb
+        ubyte from = 10
+        ubyte end = 20
+
+        for bb in from to end step 3 {
+            c64scr.print_ub(bb)
+            c64.CHROUT(',')
+        }
+        c64.CHROUT('\n')
+        for bb in end to from step -3 {
+            c64scr.print_ub(bb)
+            c64.CHROUT(',')
+        }
+        c64.CHROUT('\n')
 
         word ww
         word fromw = -10