std::nullopt
From cppreference.com
| Defined in header <optional>
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| inline constexpr nullopt_t nullopt{/*unspecified*/}; |
(since C++17) | |
std::nullopt is a constant of type std::nullopt_t. Used to indicate that an std::optional does not contain a value.
See also
| (C++17) |
indicator of an std::optional that does not contain a value (class) |