std::tuple<Types...>::swap

 

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std::tuple

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tuple::operator=

tuple::swap

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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::tuple)

get(std::tuple)

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Defined in header <tuple>
void swap( tuple& other )noexcept(/* see below */);	(1)	(since C++11) (constexpr since C++20)
constexprvoid swap(const tuple& other )noexcept(/* see below */)const;	(2)	(since C++23)

Calls swap (which might be std::swap, or might be found via ADL) for each element in *this and its corresponding element in other.

If any selected swap function call is ill-formed, or does not swap the corresponding elements of both tuples, the behavior is undefined.	(until C++23)
If any selected swap function call does not swap the corresponding elements of both tuples, the behavior is undefined. 1) The program is ill-formed if (std::is_swappable_v<Types>&& ...) is not true. 2) The program is ill-formed if (std::is_swappable_v<const Types>&& ...) is not true.	(since C++23)

Parameters

other

-

tuple of values to swap

Return value

(none)

Exceptions

noexcept specification:   noexcept(     noexcept(swap(std::declval<T0&>>(), std::declval<T0&>()))&&     noexcept(swap(std::declval<T1&>>(), std::declval<T1&>()))&&     noexcept(swap(std::declval<T2&>>(), std::declval<T2&>()))&&     ... ) 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.	(until C++17)
1) noexcept specification:   noexcept((std::is_nothrow_swappable_v<Types>&& ...)) 2) noexcept specification:   noexcept((std::is_nothrow_swappable_v<const Types>&& ...))	(since C++17)

Example

Run this code

#include <iostream>#include <string>#include <tuple>   int main(){std::tuple<int, std::string, float> p1{42, "ABCD", 2.71}, p2; p2 =std::make_tuple(10, "1234", 3.14);   auto print_p1_p2 =[&](auto rem){std::cout<< rem <<"p1 = {"<< std::get<0>(p1)<<", "<< std::get<1>(p1)<<", "<< std::get<2>(p1)<<"}, "<<"p2 = {"<< std::get<0>(p2)<<", "<< std::get<1>(p2)<<", "<< std::get<2>(p2)<<"}\n";};   print_p1_p2("Before p1.swap(p2): "); p1.swap(p2); print_p1_p2("After p1.swap(p2): "); swap(p1, p2); print_p1_p2("After swap(p1, p2): ");}

Output:

Before p1.swap(p2): p1 = {42, ABCD, 2.71}, p2 = {10, 1234, 3.14} After p1.swap(p2): p1 = {10, 1234, 3.14}, p2 = {42, ABCD, 2.71} After swap(p1, p2): p1 = {42, ABCD, 2.71}, p2 = {10, 1234, 3.14}

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

See also

std::swap(std::tuple) (C++11)	specializes the std::swap algorithm (function template)
swap (C++11)	swaps the contents (public member function of std::pair<T1,T2>)