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

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

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:

#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

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

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