<optional> functions

make_optional

Makes an object optional.

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

nullopt

inline constexpr nullopt_t nullopt(unspecified );

swap

template <class T>
    void swap(optional<T>&, optional<T>&) noexcept(see below );