Related: it’s always sort of irritated me that Java’s visibility rules conflate things in weird ways.

Take the three properties:

1. Callable by subclasses
2. Callable by code in the same package
3. Overridable

These are separate concerns, but you can’t express all combinations. In particular, you can’t express a method that can be overridden by a subclass, but can’t be called by that subclass. You also can’t avoid letting other classes in the same package call an overrideable method.

To be honest, I’m not sure I need to do that (though I mostly own the projects I work on without arbitrary users extending them, so visibility is just a code-structuring tool between “adults”, as Python puts it), but I’m still annoyed.

I find it a bit interesting this mentions lisp, but does not touch on before and after methods at all, which provide a partial resolution to the problem.

So at first I was like what the heck no I wanna extend all the time (as in I thought of a thousand times where I’ve enjoyed super/call-next-method) but then I remembered the template method pattern from Smalltalk/Java, for Lispers probably better known as

(define (frobnicate-skele proc foo bar)
  …
  (… bar (proc foo) …)
  …)

(define (frobnicate-horse horse stable)
  (frobnicate-skele (lambda (horse) …) horse stable)

The proc in the skele is the equivalent of BETA’s inner.

Fair enough, sometimes you want one and sometimes the other 🤷🏻‍♀️

I suggest adding the date (2012) to the title.