Implemented simple expressions

src/build/expression/Expression.go

@@ -55,13 +55,13 @@ func (expr *Expression) Close() {
 }
 
 // EachLeaf iterates through all leaves in the tree.
-func (expr *Expression) EachLeaf(callBack func(*Expression) error) error {
+func (expr *Expression) EachLeaf(call func(*Expression) error) error {
 	if expr.IsLeaf() {
-		return callBack(expr)
+		return call(expr)
 	}
 
 	for _, child := range expr.Children {
-		err := child.EachLeaf(callBack)
+		err := child.EachLeaf(call)
 
 		if err != nil {
 			return err
@@ -71,6 +71,28 @@ func (expr *Expression) EachLeaf(callBack func(*Expression) error) error {
 	return nil
 }
 
+// EachOperation iterates through all the operations in the tree.
+func (expr *Expression) EachOperation(call func(*Expression) error) error {
+	if expr.IsLeaf() {
+		return nil
+	}
+
+	// Don't descend into the parameters of function calls
+	if expr.Token.Text() == "λ" {
+		return call(expr)
+	}
+
+	for _, child := range expr.Children {
+		err := child.EachOperation(call)
+
+		if err != nil {
+			return err
+		}
+	}
+
+	return call(expr)
+}
+
 // RemoveChild removes a child from the expression.
 func (expr *Expression) RemoveChild(child *Expression) {
 	for i, c := range expr.Children {