856 B
856 B
[optional.hash]
22 General utilities library [utilities]
22.5 Optional objects [optional]
22.5.11 Hash support [optional.hash]
template<class T> struct hash<optional<T>>;
The specialization hash<optional> is enabled ([unord.hash]) if and only if hash<remove_const_t> is enabled.
When enabled, for an object o of type optional, if o.has_value() == true, then hash<optional>()(o) evaluates to the same value as hash<remove_const_t>()(*o); otherwise it evaluates to an unspecified value.
The member functions are not guaranteed to be noexcept.