NAME¶

std::swap(std::pair) - std::swap(std::pair)

Synopsis¶

Defined in header <utility>
template< class T1, class T2 >
(since C++11)
void swap( std::pair<T1,T2>& x, std::pair<T1,T2>& y ) (until C++20)

noexcept(/* see below */);
template< class T1, class T2 >

constexpr void swap( std::pair<T1,T2>& x, std::pair<T1,T2>& y (since C++20)
) (1)

noexcept(/* see below */);
template< class T1, class T2 >

constexpr void swap( const std::pair<T1,T2>& x, const (2) (since C++23)
std::pair<T1,T2>& y )

noexcept(/* see below */);

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. (since C++17)
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.

Parameters¶

x, y - pairs whose contents to swap

Return value¶

(none)

Exceptions¶

noexcept specification:
noexcept(noexcept(x.swap(y)))

Example¶

// Run this code

#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}

See also¶

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

Category:¶

* conditionally noexcept