std::experimental::nullopt_t (3) - Linux Manuals
std::experimental::nullopt_t: std::experimental::nullopt_t
NAME
std::experimental::nullopt_t - std::experimental::nullopt_t
Synopsis
Defined in header <experimental/optional>
struct nullopt_t; (library fundamentals TS)
std::experimental::nullopt_t is an empty class type used to indicate optional type with uninitialized state. In particular, std::experimental::optional has a constructor with nullopt_t as a single argument, which creates an optional that does not contain a value.
std::experimental::nullopt_t must be a LiteralType and cannot have a default constructor.
It must have a constexpr constructor that takes some implementation-defined literal type.
Notes
nullopt_t is not DefaultConstructible to support both op = {}; and op = nullopt; as the syntax for disengaging an optional object.
A possible implementation of this class is
See also
nullopt an object of type nullopt_t
(C++17)