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

See also

swaps the values of two objects
(function template)

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