Std::pair (3) Linux Manual Page

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

Synopsis

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)) && (until C++17)
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.
noexcept specification:
noexcept(
std::is_nothrow_swappable_v<first_type> && (since C++17)
std::is_nothrow_swappable_v<second_type>
)

Example

// Run this code

#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

std::pair (3) Linux Manual Page