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

struct nullopt_t {
constexpr nullopt_t(int) {}
};

See also¶

nullopt an object of type nullopt_t
(C++17) (constant)