std::tuple::swap(3)

NAME
std::tuple::swap - std::tuple::swap

Synopsis
   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(/* (2) (since C++23)
   see below */) const;
   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 (until C++23)
   corresponding elements of both tuples, the behavior is undefined.
   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 (since C++23)
   not true.
   2) The program is ill-formed if (std::is_swappable_v<const Types> &&
   ...) is not true.

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&>())) && (until C++17)
       ...
   )
   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.
   1)
   noexcept specification:
   noexcept((std::is_nothrow_swappable_v<Types> && ...)) (since C++17)
   2)
   noexcept specification:
   noexcept((std::is_nothrow_swappable_v<const Types> && ...))

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

Category:
     * conditionally noexcept