simpler vm

internal/object/str.go

@@ -35,17 +35,21 @@ func (s String) String() string {
 }
 
 func (s String) Add(other Object) (Object, error) {
-	if !AssertTypes(other, StringType) {
+	switch obj := other.(type) {
+	case String:
+		return String{s.Value + obj.Value}, nil
+	default:
 		return nil, NewBinaryOpError(s, other, "+")
 	}
-	return String{s.Value + other.(String).Value}, nil
 }
 
 func (s String) Mul(other Object) (Object, error) {
-	if !AssertTypes(other, IntegerType) {
+	switch obj := other.(type) {
+	case Integer:
+		return String{strings.Repeat(s.Value, int(obj.Value))}, nil
+	default:
 		return nil, NewBinaryOpError(s, other, "*")
 	}
-	return String{strings.Repeat(s.Value, int(other.(Integer).Value))}, nil
 }
 
 func (s String) Get(index Object) (Object, error) {