template <class T> void swap(T& a, T& b) noexcept(see below);
Remarks: This function 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 MoveConstructible (Table [tab:moveconstructible]) and MoveAssignable (Table [tab:moveassignable]).
Effects: Exchanges values stored in two locations.
template <class T, size_t N>
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 ([swappable.requirements]) b[i] for all i in the range [0, N).
Effects: As if by swap_ranges(a, a + N, b).