# std::bitset<N>::to_ulong

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< cpp‎ | utility‎ | bitset

unsigned long to_ulong() const |  | (until C++23)
constexpr unsigned long to_ulong() const |  | (since C++23)

Converts the contents of the bitset to an unsigned long integer.

The first bit of the bitset corresponds to the least significant digit of the number and the last bit corresponds to the most significant digit.

### Parameters

(none)

### Return value

the converted integer

### Exceptions

throws std::overflow_error if the value can not be represented in unsigned long.

### Example

Run this code

    #include <iostream>
    #include <stdexcept>
    #include <bitset>

    int main()
    {
        for (unsigned long i = 0; i < 10; ++i) {
            std::bitset<5> b(i);
            std::bitset<5> b_inverted = ~b;
            std::cout << i << '\t' << b << '\t' << b_inverted << '\t'
                      << b_inverted.to_ulong() << '\n';
        }

        std::cout << std::bitset<32>().to_string('-') << '\n';

        try {
            std::bitset<128> x(42);
            std::cout << x.to_ulong() << '\n';
            x.flip();
            std::cout << x.to_ulong() << '\n'; // throws
        } catch (const std::overflow_error& ex) {
            std::cout << "ex: " << ex.what() << '\n';
        }
    }

Possible output:

    0	00000	11111	31
    1	00001	11110	30
    2	00010	11101	29
    3	00011	11100	28
    4	00100	11011	27
    5	00101	11010	26
    6	00110	11001	25
    7	00111	11000	24
    8	01000	10111	23
    9	01001	10110	22
    --------------------------------
    42
    ex: bitset to_ulong overflow error

### See also

to_string | returns a string representation of the data (public member function)
to_ullong (C++11) | returns an unsigned long long integer representation of the data (public member function)

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