std::hash<std::string_view>, std::hash<std::wstring_view>, std::hash<std::u8string_view>, std::hash<std::u16string_view>, std::hash<std::u32string_view>
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< cpp | string | basic string view
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std::basic_string_view
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Constants
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
hash<std::string_view>hash<std::wstring_view>hash<std::u8string_view>hash<std::u16string_view>hash<std::u32string_view>
(C++20)
Deduction guides (C++20)
Defined in header
<string_view>
template<> struct hash<std::string_view >;
(since C++17)
template<> struct hash<std::wstring_view >;
(since C++17)
template<> struct hash<std::u8string_view >;
(since C++20)
template<> struct hash<std::u16string_view >;
(since C++17)
template<> struct hash<std::u32string_view >;
(since C++17)
Template specializations of std::hash for the various view classes for hashing views.
These hashes equal the hashes of corresponding std::basic_string classes: If S is one of the standard basic_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)).
[edit] Example
Run this code
#include <iostream> #include <string_view> #include <unordered_set> using namespace std::literals; int main() { std::cout << "\"A\" #: " << std::hash <std::string_view >{}("A"sv) << '\n'; std::cout << "L\"B\" #: " << std::hash <std::wstring_view >{}(L"B"sv) << '\n'; std::cout << "u8\"C\" #: " << std::hash <std::u8string_view >{}(u8"C"sv) << '\n'; std::cout << "u\"D\" #: " << std::hash <std::u16string_view >{}(u"D"sv) << '\n'; std::cout << "U\"E\" #: " << std::hash <std::u32string_view >{}(U"E"sv) << '\n'; // std::hash for string_view family makes it possible to keep these view-types // in unordered_* associative containers, such as unordered_set. But ensure // the lifespan of referenced strings is no less than lifespan of the container, // i.e. no dangling references occurred. std::unordered_set stars{"Rigel"sv, "Capella"sv, "Vega"sv, "Arcturus"sv}; for (std::string_view const& s : stars) std::cout << s << ' '; std::cout << '\n'; }
Possible output:
"A" #: 6919333181322027406 L"B" #: 11959850520494268278 u8"C" #: 12432341034569643010 u"D" #: 312659256970442235 U"E" #: 18073225910249204957 Arcturus Vega Capella Rigel