std::hash (std::string_view, std::wstring_view, std::u16string_view, std::u32string_view)
From cppreference.com
                    
                                        
                    < cpp | string | basic string view
                    
                                                            
                    | Defined in header  <string_view> | ||
| template<> struct hash<std::string_view>; template<> struct hash<std::wstring_view>; | (since C++17) | |
Template specializations of std::hash for the various view classes for hashing views.
[edit] See also
| (C++11) | hash function object (class template) |