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

    From cppreference.com
     
    C++
     
    Utilities library
    General utilities
    Relational operators (deprecated in C++20)
     
    std::tuple
     
    Defined in header <tuple> 
    void swap( tuple& other ) noexcept(/* see below */);
    		(1) (since C++11)
    (constexpr since C++20) 
    constexpr void 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

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