std::function::operator()

• If the target is a function pointer or a function object, it is called forwarding the arguments to the call.
• If the target is a pointer to a non-static member function, it is called using the first argument as the object on which the member is called (this may either be an object, a reference, or a pointer to it), and the remaining arguments are forwarded as arguments for the member function.
• If it is a pointer to a non-static data member, it should be called with a single argument, and the function returns a reference to that member of its argument (the argument may either be an object, a reference, or a pointer to it).
• If the object has no target (it is an empty function), it throws a bad_function_call exception.

Parameters

args...

Arguments for the call.
If the type of the callable object targeted by the function object is a member pointer, the first argument shall be an object for which that member is defined (or a reference, or a pointer to it).

Args... are the argument types specified in the signature used as class template parameter.

Return value

Example

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// function::operator() example
#include <iostream>     // std::cout
#include <functional>   // std::function, std::plus, std::minus, std::multiplies

int main () {
  // an array of functions:
  std::function<int(int,int)> fn[] = {
    std::plus<int>(),
    std::minus<int>(),
    std::multiplies<int>()
  };

  for (auto& x: fn) std::cout << x(10,5) << '\n';

  return 0;
}

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Data races

Exception safety

See also

function::target

Get pointer to target (public member function)

function::operator bool

Check if callable (public member function)