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Comment by tatterdemalion | Hacker News Reader

This example code must be monomorphized at compile time, meaning that each closure will have a different representation. "Tail call optimization at the type level" is not possible with this compilation model.

(The problem is solved by using a trait object to dynamically dispatch the inner call. https://play.rust-lang.org/?gist=0d3c0a5f1291eb34ba61bd39449...)

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From memory I solved it using more CPS and currying. Well manually currying with functions like curry1, curry2, etc...

Although I'm pretty sure you can overload the Fn* traits to implement currying in Rust. (Fn traits are unstable). Which is neat.

    // Something like this:
    impl<F, A, B, R> (FnOnce(A) -> Curry<F, A, B>)  for  F
        where F: FnOnce(A, B) -> R,
    { ... }

    // and
    impl<F, A, B, R> (FnOnce(B) -> R) for Curry<F, A, B>
        where F: FnOnce(A, B) -> R

I think I got it working... but you would need some work for more arguments. (And it worked different on different versions of rust-nightly :/)

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