std::function::target(3)

NAME
std::function::target - std::function::target

Synopsis
   template< class T > (1) (since C++11)
   T* target() noexcept;
   template< class T > (2) (since C++11)
   const T* target() const noexcept;
   Returns a pointer to the stored callable function target.

Parameters
   (none)

Return value
   A pointer to the stored function if target_type() == typeid(T), otherwise a null
   pointer.

Example
// Run this code
 #include <functional>
 #include <iostream>
 int f(int, int) { return 1; }
 int g(int, int) { return 2; }
 void test(std::function<int(int, int)> const& arg)
 {
     std::cout << "test function: ";
     if (arg.target<std::plus<int>>())
         std::cout << "it is plus\n";
     if (arg.target<std::minus<int>>())
         std::cout << "it is minus\n";
     int (*const* ptr)(int, int) = arg.target<int(*)(int, int)>();
     if (ptr && *ptr == f)
         std::cout << "it is the function f\n";
     if (ptr && *ptr == g)
         std::cout << "it is the function g\n";
 }
 int main()
 {
     test(std::function<int(int, int)>(std::plus<int>()));
     test(std::function<int(int, int)>(std::minus<int>()));
     test(std::function<int(int, int)>(f));
     test(std::function<int(int, int)>(g));
 }

Output:
 test function: it is plus
 test function: it is minus
 test function: it is the function f
 test function: it is the function g
   Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
      DR Applied to Behavior as published Correct behavior
   LWG 2591 C++11 the behavior is undefined if T is behavior is defined (always
                       not Callable returns nullptr)

See also
   target_type obtains the typeid of the stored target
               (public member function)