std::pair<T1,T2>::swap

void swap(pair& other) noexcept(/* see below */);		(since C++11) (until C++20)
constexpr void swap(pair& other) noexcept(/* see below */);		(since C++20)

Swaps first with other.first and second with other.second.

Parameters

other

pair of values to swap

Return value

(none).

Exceptions

`noexcept` specification: `noexcept( noexcept(swap(first, other.first)) && noexcept(swap(second, other.second)) )` In the expression above, the identifier `swap` is looked up in the same manner as the one used by the C++17 `std::is_nothrow_swappable` trait.	(until C++17)
`noexcept` specification: `noexcept( std::is_nothrow_swappable_v<first_type> && std::is_nothrow_swappable_v<second_type> )`	(since C++17)

Example

#include <iostream>
#include <utility>
#include <string>
int main()
{
    std::pair<int, std::string> p1, p2;
    p1 = std::make_pair(10, "test");
    p2.swap(p1);
    std::cout << "(" << p2.first << ", " << p2.second << ")\n";
}

Output:

(10, test)

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 2456	C++11	the `noexcept` specification is ill-formed	made to work