std::hash(std::string,std::wstring,std::u16string,std::u32string,std::pmr::string,std::pmr::wstring,std::pmr::u16string,std::pmr::u32string) (3) - Linux Manuals

std::hash(std::string,std::wstring,std::u16string,std::u32string,std::pmr::string,std::pmr::wstring,std::pmr::u16string,std::pmr::u32string): std::hash(std::string,std::wstring,std::u16string,std::u32string,std::pmr::string,std::pmr::wstring,std::pmr::u16string,std::pmr::u32string)

NAME

std::hash(std::string,std::wstring,std::u16string,std::u32string,std::pmr::string,std::pmr::wstring,std::pmr::u16string,std::pmr::u32string) - std::hash(std::string,std::wstring,std::u16string,std::u32string,std::pmr::string,std::pmr::wstring,std::pmr::u16string,std::pmr::u32string)

Synopsis

Defined in header <string>
template<> struct hash<std::string>;
template<> struct hash<std::wstring>;
template<> struct hash<std::u8string>; // c++20 (since C++11)
template<> struct hash<std::u16string>;
template<> struct hash<std::u32string>;
template<> struct hash<std::pmr::string>;
template<> struct hash<std::pmr::wstring>;
template<> struct hash<std::pmr::u8string>; (since C++20)
template<> struct hash<std::pmr::u16string>;
template<> struct hash<std::pmr::u32string>;

The template specializations of std::hash for the various string classes allow users to obtain hashes of strings.

These hashes equal the hashes of corresponding std::basic_string_view classes: If S is one of these string types, SV is the corresponding string view type, and s is an object of type S, then std::hash<S>()(s) == std::hash<SV>()(SV(s)). (since C++17)

Example

The following code shows one possible output of a hash function used on a string:
// Run this code

  #include <iostream>
  #include <string>
  #include <functional>

  int main()
  {
      std::string s = "Stand back! I've got jimmies!";
      std::hash<std::string> hash_fn;

      size_t hash = hash_fn(s);

      std::cout << hash << '\n';
  }

Output:

  325378910