get resulting type of std::bind

Question

I'm trying to get the resulting type of std::bind in combination with a lambda. I've tried the following two:

template<typename F>
typename std::result_of<std::bind(F,uint)> func(F f, uint i);

This doesn't work for whatever reason. I've also tried using decltype:

template<typename F>
decltype(std::bind(F(),uint()) func(F f, uint i);

This doesn't work, because when i use this template function with a lambda f, then it complains that lambdas have a deleted default constructor.

Can you please help me out here? I've unsuccessfully tried finding answers on the net.

Thank you!

Answer 1

I suggest using decltype(auto) as follows:

template<typename F>
decltype(auto) func(F f, uint i) { // ... }

so the return type will be deduced by compiler.

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Then, I don't think that std::result_of is an appropriate tool in this case.

But with decltype, you might also do exactly what @Jarod42 mentioned in the comment: use a trailing return type:

template<typename F>
auto func(F f, uint i) -> decltype(std::bind(f, i)) { // ... }

which should also work with C++11 (the very first solution requires C++14 support).