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

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< cpp‎ | utility‎ | tuple

Defined in header `<tuple>` |  |
| (1) |
void swap( tuple& other ) noexcept(/* see below */); |  | (since C++11) (until C++20)
constexpr void swap( tuple& other ) noexcept(/* see below */); |  | (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

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>`)

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