20 General utilities library [utilities]

20.2 Utility components [utility]

20.2.2 swap [utility.swap]

template<class T> constexpr void swap(T& a, T& b) noexcept(see below);
Remarks: This function is a designated customization point ([namespace.std]) and shall not participate in overload resolution unless is_­move_­constructible_­v<T> is true and is_­move_­assignable_­v<T> is true.
The expression inside noexcept is equivalent to:
is_nothrow_move_constructible_v<T> && is_nothrow_move_assignable_v<T>
Requires: Type T shall be Cpp17MoveConstructible (Table 26) and Cpp17MoveAssignable (Table 28).
Effects: Exchanges values stored in two locations.
template<class T, size_t N> constexpr void swap(T (&a)[N], T (&b)[N]) noexcept(is_nothrow_swappable_v<T>);
Remarks: This function shall not participate in overload resolution unless is_­swappable_­v<T> is true.
Requires: a[i] shall be swappable with b[i] for all i in the range [0, N).
Effects: As if by swap_­ranges(a, a + N, b).