std::hash (std::experimental::string_view, std::experimental::wstring_view, std::experimental::u16string_view, std::experimental::u32string_view)
From cppreference.com
                    
                                        
                    < cpp | experimental | basic string view
                    
                                                            
                    |   Defined in header  <experimental/string_view>
  | 
||
|   template<> struct hash<std::experimental::string_view>; template<> struct hash<std::experimental::wstring_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)  |