std::make_optional

 

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optional

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std::optional

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optional::optional

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optional::operator=

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optional::operator booloptional::has_value

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Defined in header <optional>
template< class T > constexpr std::optional<std::decay_t<T>> make_optional( T&& value );	(1)	(since C++17)
template< class T, class... Args > constexpr std::optional<T> make_optional( Args&&... args );	(2)	(since C++17)
template< class T, class U, class... Args > constexpr std::optional<T> make_optional( std::initializer_list<U> il, Args&&... args );	(3)	(since C++17)

1) Creates an optional object from value. Effectively calls std::optional<std::decay_t<T>>(std::forward<T>(value))

2) Creates an optional object constructed in-place from args.... Equivalent to return std::optional<T>(std::in_place, std::forward<Args>(args)...);.

3) Creates an optional object constructed in-place from il and args.... Equivalent to return std::optional<T>(std::in_place, il, std::forward<Args>(args)...);.

Parameters

value	-	the value to construct optional object with
il, args	-	arguments to be passed to the constructor of T.

Return value

The constructed optional object.

Exceptions

Throws any exception thrown by the constructor of T.

Notes

T need not be movable for overloads (2-3) due to guaranteed copy elision.

See also

(constructor)

constructs the optional object (public member function)