basic for loop + examples -> era3

core/compiler.go

@@ -153,6 +153,7 @@ func (c *Compiler) add(instruction Bytecode) {
 	c.advance(1)
 }
 
+// addConstant add both a constant (if it is not already defined), and add the index of it to the bytecode
 func (c *Compiler) addConstant(value Value) {
 	chunk := c.Chunk
 	for i := 0; i < len(chunk.Constants); i++ {
@@ -165,6 +166,10 @@ func (c *Compiler) addConstant(value Value) {
 
 	chunk.Constants = append(chunk.Constants, value)
 
+	if len(chunk.Constants) > 256 {
+		panic("too many constants (>256)")
+	}
+
 	c.add(Bytecode(len(chunk.Constants) - 1))
 }
 
@@ -472,7 +477,6 @@ func (c *Compiler) compile(tree Node) (TypeSignature, error) {
 			c.add(InstructionJumpFalse)
 			jumpValuePos = c.ip
 			c.advance(2)
-
 		}
 
 		c.add(InstructionPop)
@@ -492,6 +496,74 @@ func (c *Compiler) compile(tree Node) (TypeSignature, error) {
 
 		return &CompositeSignature{dt, &NilSignature{}}, nil
 
+	case ForNodeType:
+		n := tree.(*ForNode)
+
+		is, err := c.compile(n.iterator)
+		if err != nil {
+			return nil, err
+		}
+
+		iteratorSignature := &FunctionSignature{
+			[]TypeSignature{},
+			&TupleSignature{
+				[]TypeSignature{
+					&AnySignature{},
+					&BooleanSignature{},
+				},
+			},
+		}
+
+		if !iteratorSignature.Contains(is) {
+			return nil, c.error(fmt.Sprintf("cannot iterate with non-iterator %s (must be %s)", is, iteratorSignature), n.iterator)
+		}
+
+		outputSig := is.(*FunctionSignature).Out.(*TupleSignature).Contents[0]
+		ipos := c.ip
+
+		c.addDescend()
+		c.add(InstructionDuplicate)
+		c.add(InstructionCall)
+		c.add(InstructionDestructureTuple)
+
+		// if no more items; jump to end
+		c.add(InstructionJumpFalse)
+		jmpValuePos := c.ip
+		c.advance(2)
+
+		if n.counter.Type() != ReferenceNodeType {
+			return nil, c.error("cannot use non-variable as a counter", n.counter)
+		}
+
+		name := n.counter.(*ReferenceNode).name
+
+		c.add(InstructionDeclareLocal)
+		c.addConstant(&StringValue{
+			name,
+		})
+		c.add(InstructionPop)
+		c.registerVar(name, outputSig)
+
+		_, err = c.compile(n.logic)
+		if err != nil {
+			return nil, err
+		}
+		c.add(InstructionPop)
+
+		c.addAscend()
+
+		c.add(InstructionLoop)
+		c.addU16(uint16(c.ip - ipos + 2))
+
+		// end of loop
+		c.putU16(jmpValuePos, uint16(c.ip-jmpValuePos-2))
+
+		c.add(InstructionPop)
+		c.add(InstructionPop)
+		c.add(InstructionNil)
+
+		return &NilSignature{}, nil
+
 	case AssignNodeType:
 		n := tree.(*AssignNode)