# std::hash<std::bitset>

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< cpp‎ | utility‎ | 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

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

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