20 General utilities library [utilities]

20.6 Optional objects [optional]

20.6.9 Specialized algorithms [optional.specalg]

template <class T> void swap(optional<T>& x, optional<T>& y) noexcept(noexcept(x.swap(y)));

Effects: Calls x.swap(y).

Remarks: This function shall not participate in overload resolution unless is_move_constructible_v<T> is true and is_swappable_v<T> is true.

template <class T> constexpr optional<decay_t<T>> make_optional(T&& v);

Returns: optional<decay_t<T>>(std::forward<T>(v)).

template <class T, class...Args> constexpr optional<T> make_optional(Args&&... args);

Effects: Equivalent to: return optional<T>(in_place, std::forward<Args>(args)...);

template <class T, class U, class... Args> constexpr optional<T> make_optional(initializer_list<U> il, Args&&... args);

Effects: Equivalent to: return optional<T>(in_place, il, std::forward<Args>(args)...);