This has by far the best discussion of the visitor pattern I've yet to come across.
replies(3):
https://craftinginterpreters.com/representing-code.html#the-...
I remember reading through it and not understanding why it had to be this complicated and then just used a tagged union instead.
Maybe I'm too stupid for OO. But I think that's kind of the point of the grug article as well. Why burden ourselves with indirection and complexity when there's a more straight forward way?
https://prog2.de/book/sec-java-expr-problem.html - Not the writeup I was looking for but seems to cover it well.
> Why burden ourselves with indirection and complexity when there's a more straight forward way?
Because each way has its own tradeoffs that make it more or less difficult to use in particular circumstances.
https://homepages.inf.ed.ac.uk/wadler/papers/expression/expr... - Wadler's description of the expression problem.
However, this is just not something that I typically perceive as a problem. For example in the book that I mentioned above, I didn't feel the need to use it at all. I just added the fields or the functions that were required.
In the first link you provided, the OCaml code seems to use unions as well (I don't know the language). I assume OCaml checks for exhaustive matching, so it seems extremely straight forward to extend this code.
On the other hand I have absolutely no issues with a big switch case in a more simple language. I just had a look at the code I wrote quite a while ago and it looks fine.