std::experimental::nullopt_t (3) - Linux Manuals

std::experimental::nullopt_t: std::experimental::nullopt_t


std::experimental::nullopt_t - std::experimental::nullopt_t


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.


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