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std::swap(std::pair)

From cppreference.com
< cpp‎ | utility‎ | pair
 
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
(C++20)(C++20)(C++20)  
(C++20)
(C++20)
(C++14)
(C++11)
(C++11)
(C++23)
(C++11)
(C++17)
Common vocabulary types
(C++11)
(C++17)
(C++17)
(C++17)
(C++11)
(C++17)
(C++23)


 
 
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)

[edit] Parameters

x, y - pairs whose contents to swap

[edit] Return value

(none)

[edit] Exceptions

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

[edit] 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}

[edit] See also

swaps the values of two objects
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
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