variables are reset to their declared value when entering the scope again

compiler/examples/cube3d.p8

@@ -36,8 +36,7 @@
             _vm_gfx_text(8, 6, 1, "Spin")
             _vm_gfx_text(29, 11, 1, "to Win !")
 
-            byte i
-            for i in 0 to width//10 {
+            for byte i in 0 to width//10 {
                 _vm_gfx_line(i*2+width//2-width//10, 130, i*10.w, 199, 6)
             }
 
@@ -109,7 +108,6 @@
             _vm_gfx_pixel(sx-1, sy+1, color)
             _vm_gfx_pixel(sx, sy+1, color)
             _vm_gfx_pixel(sx+1, sy+1, color)
-
             _vm_gfx_pixel(sx, sy-2, color)
             _vm_gfx_pixel(sx+2, sy, color)
             _vm_gfx_pixel(sx, sy+2, color)

compiler/examples/mandelbrot.p8

@@ -15,17 +15,13 @@
 
             for word pixelx in xoffset to xoffset+width-1 {
                 float xx = flt((pixelx-xoffset))/width/3.0+0.2
-                float xsquared
-                float ysquared
-                float x
-                float y
-                byte iter  ; @todo re-initialize variable when entering scope
 
-                x = 0.0
-                y = 0.0
-                xsquared = 0
-                ysquared = 0
-                iter = 0
+                float xsquared = 0.0
+                float ysquared = 0.0
+                float x = 0.0
+                float y = 0.0
+                byte iter = 0
+
                 while (iter<32 and xsquared+ysquared<4.0) {
                     y = x*y*2.0 + yy
                     x = xsquared - ysquared + xx
@@ -37,10 +33,8 @@
                 _vm_gfx_pixel(pixelx, pixely, iter)
             }
         }
-
         _vm_gfx_text(11, 21, 1, "Finished!")
     }
-
 }
 
 

compiler/examples/test.p8

@@ -4,15 +4,46 @@
 
 ~ main {
 
+    byte mainb = 44
+
 sub start() {
+    test()
+    test()
+}
 
-    ; word [20] prime_numbers = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71]   ; todo array_w!!!
-    word [20] fibonacci_numbers = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181]
+sub test() {
 
-    for word fibnr in fibonacci_numbers {
-        _vm_write_num(fibnr)
+    ; @todo test assigning values to array vars
+    ; @todo test creating const array vars
+
+
+    byte subb=42
+
+    for byte i in 0 to 2 {
+        float ff=3.3
+        byte bb=99
+        word ww=1999
+
+        _vm_write_num(ff)
         _vm_write_char('\n')
+        _vm_write_num(bb)
+        _vm_write_char('\n')
+        _vm_write_num(ww)
+        _vm_write_char('\n')
+        _vm_write_num(subb)
+        _vm_write_char('\n')
+        _vm_write_num(mainb)
+        _vm_write_char('\n')
+        _vm_write_char('\n')
+
+        ff += 3
+        bb += 3
+        ww += 3
+        subb += 3
+        mainb += 3
     }
+
+    return
 }
 
 }

compiler/src/prog8/ast/AST.kt

@@ -623,7 +623,7 @@ class VarDecl(val type: VarDeclType,
 }
 
 
-class Assignment(var target: AssignTarget, val aug_op : String?, var value: IExpression, override val position: Position) : IStatement {
+open class Assignment(var target: AssignTarget, val aug_op : String?, var value: IExpression, override val position: Position) : IStatement {
     override lateinit var parent: Node
 
     override fun linkParents(parent: Node) {
@@ -639,6 +639,12 @@ class Assignment(var target: AssignTarget, val aug_op : String?, var value: IExp
     }
 }
 
+// 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: IExpression, position: Position)
+    : Assignment(target, aug_op, value, position)
+
+
 data class AssignTarget(val register: Register?,
                         val identifier: IdentifierReference?,
                         val arrayindexed: ArrayIndexedExpression?,

compiler/src/prog8/ast/StmtReorderer.kt

@@ -95,22 +95,23 @@ class StatementReorderer(private val namespace: INameScope, private val heap: He
 
     override fun process(decl: VarDecl): IStatement {
         super.process(decl)
-        if(decl.type==VarDeclType.VAR || decl.type==VarDeclType.CONST) {
-            if(decl.value!=null && decl.value?.constValue(namespace, heap)==null) {
-                // the value assigned to the variable isn't a constant.
+        if(decl.type!=VarDeclType.VAR || decl.value==null)
+            return decl
+
+        // for variables that are not on the heap (so: byte, word, float),
         // replace the var decl with an assignment and add a new vardecl with the default constant value.
+        if(decl.datatype == DataType.BYTE || decl.datatype==DataType.WORD || decl.datatype==DataType.FLOAT) {
             val scope = decl.definingScope()
             if(scope !in vardeclsToAdd)
                 vardeclsToAdd[scope] = mutableListOf()
             vardeclsToAdd[scope]!!.add(decl.asDefaultValueDecl())
-                return Assignment(
+            return VariableInitializationAssignment(
                     AssignTarget(null, IdentifierReference(decl.scopedname.split("."), decl.position), null, decl.position),
                     null,
                     decl.value!!,
                     decl.position
             )
         }
-        }
         return decl
     }
 }

compiler/src/prog8/compiler/Compiler.kt

@@ -389,6 +389,7 @@ private class StatementTranslator(private val stackvmProg: StackVmProgram,
             when (stmt) {
                 is Label -> translate(stmt)
                 is Return -> translate(stmt)
+                is VariableInitializationAssignment -> translate(stmt)        // for initializing vars in a scope
                 is Assignment -> translate(stmt)        // normal and augmented assignments
                 is PostIncrDecr -> translate(stmt)
                 is Jump -> translate(stmt)
@@ -1174,6 +1175,13 @@ private class StatementTranslator(private val stackvmProg: StackVmProgram,
         }
     }
 
+
+    private fun translate(stmt: VariableInitializationAssignment) {
+        // this is an assignment to initialize a variable's value in the scope.
+        // the compiler can perhaps optimize this phase.
+        translate(stmt as Assignment)
+    }
+
     private fun translate(stmt: Assignment) {
         stackvmProg.line(stmt.position)
         translate(stmt.value)

docs/source/programming.rst

@@ -298,12 +298,15 @@ The largest 5-byte MFLPT float that can be stored is: **1.7014118345e+38**   (ne
 Initial values across multiple runs of the program
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-.. todo::
-    The initial values of your variables will be restored automatically when the program is (re)started,
-    *except for string variables, arrays and matrices*. It is assumed these are left unchanged by the program.
-    If you do modify them in-place, you should take care yourself that they work as
-    expected when the program is restarted.
+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.
 
+This only works for simple types, *and not for string variables, arrays and matrices*.
+It is assumed these are left unchanged by the program.
+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)
 
 
 Indirect addressing and address-of