Implementing Haskell's Maybe Monad in c++11

Question

I am trying to implement the Maybe monad from Haskell using the lambda functions in C++11 and templates. Here\'s what I have so far

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Answer 1

The type of a lambda isn't a specialization of std::function. It's some unamed type. There is a conversion to std::function, but that means type deduction won't work for it. So, in this call:

Maybe p = (x >>= z);

The type T2 can't be deduced:

Maybe operator>>=(Maybe t, std::function < Maybe (T1)> &f)

Store the lambda in a std::function variable from the start, and it should work:

std::function < Maybe (int)> z = [](int a) -> Maybe { ... };

However, it's probably easier to accept any kind of function object. That way you can still use auto for the lambda.

template
typename std::result_of::type
operator>>=(Maybe t, F&& f) {
    ... std::forward(f)(t.data);
}