std:: hash (std::experimental::string_view, std::experimental::wstring_view, std::experimental::u16string_view, std::experimental::u32string_view)

From cppreference.com
template <> struct hash < std:: experimental :: string_view > ;

template <> struct hash < std:: experimental :: wstring_view > ;
template <> struct hash < std:: experimental :: u16string_view > ;

template <> struct hash < std:: experimental :: u32string_view > ;
(library fundamentals TS)

Template specializations of std::hash for the various view classes for hashing views.

See also

(C++11)
hash function object
(class template)