std::experimental::nullopt_t
From cppreference.com
< cpp | experimental | optional
Defined in header <experimental/optional>
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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.
[edit] 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) {} };
[edit] See also
(library fundamentals TS) |
an object of type nullopt_t (function) |