std::swap(std::pair)

Since C++20

Header: <utility>

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

# Declarations

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 */);

(since C++23)

# Parameters

# Return value

(none)

# 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): ");
}

# See also