std::nullopt_t(3) C++ Standard Libary std::nullopt_t(3) NAME std::nullopt_t - std::nullopt_t Synopsis Defined in header <optional> struct nullopt_t; (since C++17) std::nullopt_t is an empty class type used to indicate optional type with uninitialized state. In particular, std::optional has a constructor with nullopt_t as a single argument, which creates an optional that does not contain a value. std::nullopt_t must be a non-aggregate LiteralType and cannot have a de- fault constructor or an initializer-list constructor. It must have a constexpr constructor that takes some implementation-de- fined literal type. Notes The constraints on nullopt_t's constructors exist 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 explicit nullopt_t(int) {} }; See also nullopt an object of type nullopt_t (C++17) (constant) http://cppreference.com 2024.06.10 std::nullopt_t(3)
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