akasakaR's blog

What is a Y_combinator
By akasakaR, history, 4 months ago, In English

What is a Y combinator where I see some ppl using it, it looks something like this:

template<class F>
struct y_combinate_t {
  F f;
  template<class...Args>
  decltype(auto) operator()(Args&&...args)const {
    return f(*this, std::forward<Args>(args)...);
  }
};
template<class F>
y_combinate_t<std::decay_t<F>> y_combinate( F&& f ) {
  return {std::forward<F>(f)};
};
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4 months ago, # |
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It's a workaround for recursive lambdas (see here). I personally use std::function which can be called within itself.

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    4 months ago, # ^ |
    ← Rev. 3   Vote: I like it +16 Vote: I do not like it

    Using std::function runs the risk of TLEing, for most competitive programming purposes it is way better to use self-referential lambdas or y_combinator (which is a wrapper for self-referential lambdas, though sometimes optimizations don't see through this wrapper).

    C++23 has a feature called deducing this which is a pretty good replacement for these gymnastics (in fact, it was meant to do other things but it having this property is a nice side effect).

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      4 months ago, # ^ |
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      Interesting, although I have not experienced TLEs in the past.

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4 months ago, # |
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aryanc403 wrote a blog about it , you can find it here.

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4 months ago, # |
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https://www.ycombinator.com/

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