std:: hash <std::bitset>

From cppreference.com
C++
Utilities library
General utilities
Relational operators (deprecated in C++20)
std::bitset
Defined in header <bitset>
template < std:: size_t N >
struct hash < std:: bitset < N >> ;
(since C++11)

The template specialization of std::hash for std:: bitset < N > allows users to obtain hashes of objects of type std:: bitset < N > .

Example

The following code shows one possible output of a hash function used on several bitsets:

Run this code 
#include <bitset>
#include <functional>
#include <iostream>
 
int main()
{
    std::bitset<4> b1{0}, b2{42};
    std::bitset<8> b3{0}, b4{42};
 
    std::hash<std::bitset<4>> hash_fn4;
    std::hash<std::bitset<8>> hash_fn8;
    using bin64 = std::bitset<64>;
 
    std::cout << std::hex
              << bin64{hash_fn4(b1)} << " = " << hash_fn4(b1) << '\n'
              << bin64{hash_fn4(b2)} << " = " << hash_fn4(b2) << '\n'
              << bin64{hash_fn8(b3)} << " = " << hash_fn8(b3) << '\n'
              << bin64{hash_fn8(b4)} << " = " << hash_fn8(b4) << '\n';
}

Possible output: 

0110110100001001111011100010011011010101100001100011011000011001 = 6d09ee26d5863619
1111111101011100010110100000111000111110100000111011100011110000 = ff5c5a0e3e83b8f0
0110110100001001111011100010011011010101100001100011011000011001 = 6d09ee26d5863619
0101110000011100011110011010111011100110010000110100110001001101 = 5c1c79aee6434c4d

See also

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