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)