std::nullopt

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std::optional

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nullopt_t

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nullopt

in_place

Defined in header <optional>
inline constexpr nullopt_t nullopt{/*unspecified*/};		(since C++17)

std::nullopt is a constant of type std::nullopt_t that is used to indicate optional type with uninitialized state.

See also

nullopt_t (C++17)

indicator of optional type with uninitialized state (class)