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std::swap(std::pair)

Defined in header `<utility>`
	(1)
template< class T1, class T2 > void swap( std::pair<T1,T2>& x, std::pair<T1,T2>& y ) noexcept(/* see below */);		(since C++11) (until C++20)
template< class T1, class T2 > constexpr void swap( std::pair<T1,T2>& x, std::pair<T1,T2>& y ) noexcept(/* see below */);		(since C++20)
template< class T1, class T2 > constexpr void swap( const std::pair<T1,T2>& x, const std::pair<T1,T2>& y ) noexcept(/* see below */);	(2)	(since C++23)

Swaps the contents of x and y. Equivalent to x.swap(y).

1) This overload participates in overload resolution only if std::is_swappable_v<first_type> && std::is_swappable_v<second_type> is true. 2) This overload participates in overload resolution only if std::is_swappable_v<const first_type> && std::is_swappable_v<const second_type> is true. (since C++17)

Parameters

x, y

pairs whose contents to swap

Return value

(none).

Exceptions

noexcept specification:

noexcept(noexcept(x.swap(y)))

Example

#include <iostream>
#include <utility>
 
int main()
{
    auto p1 = std::make_pair(10, 3.14);
    auto p2 = std::pair(12, 1.23); // CTAD, since C++17
 
    auto print_p1_p2 = [&](auto msg) {
        std::cout << msg
                  << "p1 = {" << std::get<0>(p1)
                  << ", "     << std::get<1>(p1) << "}, "
                  << "p2 = {" << std::get<0>(p2)
                  << ", "     << std::get<1>(p2) << "}\n";
    };
 
    print_p1_p2("Before p1.swap(p2): ");
    p1.swap(p2);
    print_p1_p2("After  p1.swap(p2): ");
    std::swap(p1, p2);
    print_p1_p2("After swap(p1, p2): ");
}

Output:

Before p1.swap(p2): p1 = {10, 3.14}, p2 = {12, 1.23}
After  p1.swap(p2): p1 = {12, 1.23}, p2 = {10, 3.14}
After swap(p1, p2): p1 = {10, 3.14}, p2 = {12, 1.23}

swap	swaps the values of two objects (function template)
std::swap(std::tuple) (C++11)	specializes the `std::swap` algorithm (function template)

std::swap(std::pair)

Parameters

Return value

Exceptions

Example

See also