add objects.Callable

objects/builtin_function.go

@@ -4,28 +4,34 @@ import (
 	"github.com/d5/tengo/token"
 )
 
-type BuiltinFunction BuiltinFunc
+type BuiltinFunction struct {
+	Value BuiltinFunc
+}
 
-func (o BuiltinFunction) TypeName() string {
+func (o *BuiltinFunction) TypeName() string {
 	return "builtin-function"
 }
 
-func (o BuiltinFunction) String() string {
+func (o *BuiltinFunction) String() string {
 	return "<builtin-function>"
 }
 
-func (o BuiltinFunction) BinaryOp(op token.Token, rhs Object) (Object, error) {
+func (o *BuiltinFunction) BinaryOp(op token.Token, rhs Object) (Object, error) {
 	return nil, ErrInvalidOperator
 }
 
-func (o BuiltinFunction) Copy() Object {
-	return BuiltinFunction(o)
+func (o *BuiltinFunction) Copy() Object {
+	return &BuiltinFunction{Value: o.Value}
 }
 
-func (o BuiltinFunction) IsFalsy() bool {
+func (o *BuiltinFunction) IsFalsy() bool {
 	return false
 }
 
-func (o BuiltinFunction) Equals(x Object) bool {
+func (o *BuiltinFunction) Equals(x Object) bool {
 	return false
 }
+
+func (o *BuiltinFunction) Call(args ...Object) (Object, error) {
+	return o.Value(args...)
+}

objects/callable.go

@@ -0,0 +1,5 @@
+package objects
+
+type Callable interface {
+	Call(args ...Object) (ret Object, err error)
+}

vm/vm.go

@@ -840,8 +840,8 @@ func (v *VM) executeCall(numArgs int) error {
 		return v.callFunction(callee.Fn, callee.Free, numArgs)
 	case *objects.CompiledFunction:
 		return v.callFunction(callee, nil, numArgs)
-	case objects.BuiltinFunction:
-		return v.callBuiltinFunction(callee, numArgs)
+	case objects.Callable:
+		return v.callCallable(callee, numArgs)
 	default:
 		return fmt.Errorf("calling non-function: %s", callee.TypeName())
 	}
@@ -864,19 +864,21 @@ func (v *VM) callFunction(fn *objects.CompiledFunction, freeVars []*objects.Obje
 	return nil
 }
 
-func (v *VM) callBuiltinFunction(builtin objects.BuiltinFunction, numArgs int) error {
+func (v *VM) callCallable(callable objects.Callable, numArgs int) error {
 	var args []objects.Object
 	for _, arg := range v.stack[v.sp-numArgs : v.sp] {
 		args = append(args, *arg)
 	}
 
-	res, err := builtin(args...)
+	res, err := callable.Call(args...)
 	v.sp -= numArgs + 1
 
+	// runtime error
 	if err != nil {
 		return err
 	}
 
+	// nil return -> undefined
 	if res == nil {
 		res = undefinedObj
 	}
@@ -933,6 +935,6 @@ func selectorAssign(dst, src *objects.Object, selectors []interface{}) error {
 func init() {
 	builtinFuncs = make([]objects.Object, len(objects.Builtins))
 	for i, b := range objects.Builtins {
-		builtinFuncs[i] = objects.BuiltinFunction(b.Func)
+		builtinFuncs[i] = &objects.BuiltinFunction{Value: b.Func}
 	}
 }