Halt to halt the VM

internal/vm/vm.go

@@ -686,7 +686,7 @@ func (vm *VM) LastPoppedStackElem() object.Object {
 	return vm.stack[vm.sp]
 }
 
-func (vm *VM) Run() error {
+func (vm *VM) Run() (err error) {
 	var n int
 	var ip int
 	var ins code.Instructions
@@ -699,9 +699,7 @@ func (vm *VM) Run() error {
 		}()
 	}
 
-	var err error
-
-	for vm.frame.ip < len(vm.frame.Instructions())-1 && err == nil {
+	for err == nil {
 		vm.frame.ip++
 
 		ip = vm.frame.ip
@@ -894,6 +892,9 @@ func (vm *VM) Run() error {
 		case code.OpMinus:
 			err = vm.executeMinus()
 
+		case code.OpHalt:
+			return
+
 		default:
 			err = fmt.Errorf("unhandled opcode: %s", op)
 		}