std::function<R(Args...)>::target (3) - Linux Manuals

std::function<R(Args...)>::target: std::function<R(Args...)>::target

NAME

std::function<R(Args...)>::target - std::function<R(Args...)>::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