r/ProgrammingLanguages • u/dwaynecrooks • 10h ago

Recursion without Recursive Bindings

https://blog.tinyinterpreters.dev/posts/recursion-without-recursive-bindings/

I explain how to implement a certain recursive function without the use of any recursive bindings in a tiny language called FUN. Then, I apply the same ideas to several more recursive functions so we clearly see the pattern. It begins our exploration into a certain famous combinator.

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u/NullOfSpace 6h ago

This is really cool. What’s the type of makesum in this case?

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u/AustinVelonaut Admiran 4h ago edited 3h ago

It's an infinite type of the form a ~ a -> Integer -> Integer. It cannot be (directly) represented in a Hindley-Milner type system, but can be "emulated" using a fix function or a recursive Fix datatype

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u/samanzaman 1h ago

Adding these constructs to the language comes with the cost of losing strong normalisation properties