That's why we usually group all of these handlers into a single Visitor interface. Then you only add one class and one extra method to the Visitor, and all the

That's why we usually group all of these handlers into a single Visitor interface. Then you only add one class and one extra method to the Visitor, and all the other variants stay the same. You're brushing up against the so-called "expression problem", though, where you can choose between adding types easily or adding algorithms easily, but not usually both.