std::hash(std::string,std::wstring,std::u16string,std::u32string,std::pmr::string,std::pmr::wstring,std::pmr::u16string,std::pmr::u32string) (3) Linux Manual Page

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

See also

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