This reminds me of this article: "The visitor pattern is essentially the same thing as Church Encoding" [0], although I think this comment [1] and this one [2]

This reminds me of this article: "The visitor pattern is essentially the same thing as Church Encoding" [0], although I think this comment [1] and this one [2] on HN explain it better. The article is written in Haskell, but it's basically saying that, because object-oriented programming languages lacked sum types, the visitor pattern makes the transform from (a | b | c) -> T to (a -> T, b -> T, c -> T) -> T where (a | b | c) is a sum type saying "it can be either a of type a, type b, or type c", and (a -> T, b-> T, c -> T) is a stand-in for a record of functions (i.e. the v-table of an instance of a visitor class). [0]: https://www.haskellforall.com/2021/01/the-visitor-pattern-is-essentially-same.html https://www.haskellforall.com/2021/01/the-visitor-pattern-is... [1]: https://news.ycombinator.com/item?id=26034790 https://news.ycombinator.com/item?id=26034790 [2]: https://news.ycombinator.com/item?id=26024600 https://news.ycombinator.com/item?id=26024600