std::swap(std::pair)

 

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std::pair

Member functions

pair::pair

pair::operator=

pair::swap (C++11)

Non-member functions

make_pair

operator==operator!=operator<operator<=operator>operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

swap(std::pair) (C++11)

get(std::pair) (C++11)

Helper classes

tuple_size<std::pair> (C++11)

tuple_element<std::pair> (C++11)

basic_common_reference<std::pair> (C++23)

common_type<std::pair> (C++23)

formatter<std::pair> (C++23)

piecewise_construct_t (C++11)

Deduction guides(C++17)

 

Defined in header <utility>
	(1)
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 */);		(2)	(since C++23)

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. 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.

(since C++17)

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) (C++11)	specializes the std::swap algorithm (function template)