23 General utilities library [utilities]

23.6 Optional objects [optional]

23.6.9 Specialized algorithms [optional.specalg]

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

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Effects: Calls x.swap(y).

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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);

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

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

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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);

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