c++ - Determine the argument and result Type of a functor -

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how can test whether functor callable object takes reference int , returns bool?

template<typename functor> void foo(functor f) {     static_assert('functor == bool (int&)', "error message");      int x = -1;     if (f(x))         std::cout << x << std::endl; }  bool bar(int& x) {     x = 4711;     return true; }  struct other {     bool operator()(int& x)     {         x = 815;         return true;     } };

looks me don't want check signature of functor, want restrict user can pass in, in first place:

if have access std::function can this:

void foo(const std::function<bool(int&)>& f)

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