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Difference between revisions of "cpp/utility/pair/swap2"

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< cpp‎ | utility‎ | pair
(Created page with "{{cpp/title | swap<small>(std::pair</small>}} {{cpp/utility/pair/sidebar}} {{ddcl list begin}} {{ddcl list item | template<class T1, class T2> void swap(pair<T1, T2>& x, pair<T1,...")
 
m (fmt.)
 
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{{cpp/title | swap<small>(std::pair</small>}}
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{{cpp/title|swap<small>(std::pair)</small>}}
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{{cpp/utility/pair/sidebar}}
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{{cpp/utility/pair/navbar}}
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{{ddcl list begin}}
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{{dcl begin}}
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{{ddcl list item |
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{{dcl header|utility}}
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template<class T1, class T2>
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{{dcl rev multi|num=1
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void swap(pair<T1, T2>& x, pair<T1, T2>& y);
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|since1=c++11|dcl1=
 +
template< class T1, class T2 >
 +
void swap( std::pair<T1,T2>& x, std::pair<T1,T2>& y )
 +
    noexcept(/* see below */);
 +
|since2=c++20|dcl2=
 +
template< class T1, class T2 >
 +
constexpr void swap( std::pair<T1,T2>& x, std::pair<T1,T2>& y )
 +
    noexcept(/* see below */);
 
}}
 
}}
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{{ddcl list end}}
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{{dcl|num=2
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|since=c++23|
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template< class T1, class T2 >
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constexpr void swap( const std::pair<T1,T2>& x, const std::pair<T1,T2>& y )
 +
    noexcept(/* see below */);
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}}
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{{dcl end}}
  
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Swaps the contents of {{tt|lhs}} and {{tt|rhs}}. Eqiivalent to {{cpp|lhs.swap(rhs)}}.
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Swaps the contents of {{tt|x}} and {{tt|y}}. Equivalent to {{c|x.swap(y)}}.
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{{rrev|since=c++17|
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@1@ {{cpp/enable_if|{{c|std::is_swappable_v<first_type> && std::is_swappable_v<second_type>}} is {{c|true}}}}.
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@2@ {{cpp/enable_if|{{c|std::is_swappable_v<const first_type> && std::is_swappable_v<const second_type>}} is {{c|true}}}}.
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}}
  
 
===Parameters===
 
===Parameters===
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{{param list begin}}
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{{par begin}}
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{{param list item | lhs, rhs | pairs whose contents to swap}}
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{{par|x, y|pairs whose contents to swap}}
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{{param list end}}  
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{{par end}}
  
 
===Return value===
 
===Return value===
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{{return none}}
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(none)
  
 
===Exceptions===
 
===Exceptions===
 
{{noexcept|noexcept(x.swap(y))}}
 
{{noexcept|noexcept(x.swap(y))}}
 +
 +
===Example===
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{{example|
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|code=
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#include <iostream>
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#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
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                  << "p1 = {" << std::get<0>(p1)
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                  << ", "    << std::get<1>(p1) << "}, "
 +
                  << "p2 = {" << std::get<0>(p2)
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                  << ", "    << std::get<1>(p2) << "}\n";
 +
    };
 +
 +
    print_p1_p2("Before p1.swap(p2): ");
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    p1.swap(p2);
 +
    print_p1_p2("After  p1.swap(p2): ");
 +
    std::swap(p1, p2);
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    print_p1_p2("After swap(p1, p2): ");
 +
}
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|output=
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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===
 
===See also===
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{{dsc begin}}
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{{dsc inc|cpp/algorithm/dsc swap}}
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{{dsc inc|cpp/utility/tuple/dsc swap2}}
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{{dsc end}}
  
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{{dcl list begin}}
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{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
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{{dcl list end}}
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Latest revision as of 15:55, 4 January 2023

 
C++
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
std::pair
 
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)

Contents

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