rearrange builtins

builtins/exit.go

@@ -0,0 +1,19 @@
+package builtins
+
+import "monkey/object"
+
+// Exit ...
+func Exit(args ...object.Object) object.Object {
+	var status int
+	if len(args) == 1 {
+		if args[0].Type() != object.INTEGER_OBJ {
+			return newError("argument to `exit` must be INTEGER, got %s",
+				args[0].Type())
+		}
+		status = int(args[0].(*object.Integer).Value)
+	}
+
+	object.ExitFunction(status)
+
+	return nil
+}