allow destructuring tuples when assigning

core/compiler.go

@@ -569,23 +569,13 @@ func (c *Compiler) compile(tree Node) (TypeSignature, error) {
 	case AssignNodeType:
 		n := tree.(*AssignNode)
 
-		switch n.dest.Type() {
-		case ReferenceNodeType:
-			d := n.dest.(*ReferenceNode)
-
-			if d.name == "_" {
-				return c.compile(n.value)
-			}
-
-			if n.declare && c.isVarDeclaredHere(d.name) {
-				return nil, c.error(fmt.Sprintf("%s is already declared in this scope", d.name), n)
-			}
-
-			return c.addSetVar(d.name, n.value, n.declare)
-		default:
-			return nil, c.error(fmt.Sprintf("cannot assign to %s", n.dest.Type()), n.dest)
+		t, err := c.compile(n.value)
+		if err != nil {
+			return nil, err
 		}
 
+		return c.compileAssignFromStack(n.dest, t, n.declare)
+
 	case InvokeNodeType:
 		n := tree.(*InvokeNode)
 
@@ -635,6 +625,7 @@ func (c *Compiler) compile(tree Node) (TypeSignature, error) {
 
 		// allow self-referencing
 		sig := n.Signature()
+		c.descend()
 		c.registerVar(n.name, sig)
 
 		// keep track of main chunk
@@ -672,6 +663,7 @@ func (c *Compiler) compile(tree Node) (TypeSignature, error) {
 			return nil, c.error(fmt.Sprintf("yield does not match expected return; got %s, expected %s", yield, c.expectedReturn), causer)
 		}
 
+		c.ascend()
 		c.ascend()
 
 		mc.Constants[fi] = &FunctionValue{
@@ -907,6 +899,51 @@ func (c *Compiler) compileBinary(binary *BinaryNode) (TypeSignature, error) {
 	return res, nil
 }
 
+// compileAssignFromStack assign the value of type sig which is expected to be on top of the stack.
+func (c *Compiler) compileAssignFromStack(to Node, sig TypeSignature, declare bool) (TypeSignature, error) {
+	switch to.Type() {
+	case ReferenceNodeType:
+		d := to.(*ReferenceNode)
+
+		if d.name == "_" {
+			return sig, nil
+		}
+
+		if declare && c.isVarDeclaredHere(d.name) {
+			return nil, c.error(fmt.Sprintf("%s is already declared in this scope", d.name), to)
+		}
+
+		return c.addSetVar(d.name, sig, declare, to)
+	case TupleNodeType:
+		t := to.(*TupleNode)
+
+		tsig, ok := sig.(*TupleSignature)
+		if !ok {
+			return nil, c.error(fmt.Sprintf("cannot destructure non-tuple %s", sig), to)
+		}
+
+		if len(t.items) != len(tsig.Contents) {
+			return nil, c.error(fmt.Sprintf("not same amount of items; must be %d", len(tsig.Contents)), to)
+		}
+
+		c.add(InstructionDuplicate)
+		c.add(InstructionDestructureTuple)
+
+		// iterate from top to bottom
+		for i := len(t.items) - 1; i >= 0; i-- {
+			_, err := c.compileAssignFromStack(t.items[i], tsig.Contents[i], declare)
+			if err != nil {
+				return nil, err
+			}
+			c.add(InstructionPop)
+		}
+
+		return sig, nil
+	default:
+		return nil, c.error(fmt.Sprintf("cannot assign to %s", to.Type()), to)
+	}
+}
+
 func (c *Compiler) getVarSignature(name string, causer Node) (TypeSignature, error) {
 	if c.isGlobal(name) {
 		return SignatureOf(DefaultGlobals[name]), nil
@@ -950,23 +987,20 @@ func (c *Compiler) addGetVar(name string, causer Node) (TypeSignature, error) {
 	return c.getVarSignature(name, causer)
 }
 
-func (c *Compiler) addSetVar(name string, value Node, declare bool) (TypeSignature, error) {
-	t, err := c.compile(value)
-	if err != nil {
-		return nil, err
-	}
-
+// addSetVar add instructions for setting a variable of specified type which is ON TOP OF THE STACK
+// does also register the variable with the correct type.
+func (c *Compiler) addSetVar(name string, t TypeSignature, declare bool, causer Node) (TypeSignature, error) {
 	if declare {
 		c.add(InstructionDeclareLocal)
 		c.registerVar(name, t)
 	} else {
-		vt, err := c.getVarSignature(name, value)
+		vt, err := c.getVarSignature(name, causer) // it needs someone to blame >:3
 		if err != nil {
 			return nil, err
 		}
 
 		if !vt.Contains(t) {
-			return nil, c.error(fmt.Sprintf("cannot assign value of type %s to variable %s of type %s", t, name, vt), value)
+			return nil, c.error(fmt.Sprintf("cannot assign value of type %s to variable %s of type %s", t, name, vt), causer)
 		}
 
 		c.add(InstructionSetLocal)

examples/fib.ang

@@ -1,8 +1,21 @@
 
 # calculate fibonacci numbers with a loop
 
-(a, b) := (1, 0)
-for _ in 0..100 {
-    (a, b) = (a + b, b)
+fn range(from: int, to: int) -> (fn() -> (int, bool)) {
+    i := from - 1
+    end := to - 1
+
+    fn() -> (int, bool) {
+        if i < end {
+            (i = i+1, true)
+        } else {
+            (-1, false)
+        }
+    }
+}
+
+(a, b) := (0, 1)
+for _ in range(0, 100) {
+    (a, b) = (a + b, a)
     println(a)
 }