std::bitset::count

C++

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initializer_list (C++11)
bitset
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std::bitset

Member types

bitset::reference

Member functions

bitset::bitset

bitset::operator==bitset::operator!=

Element access

bitset::operator[]

bitset::test

bitset::allbitset::anybitset::none (C++11)

bitset::count

Capacity

bitset::size

Modifiers

bitset::operator&=bitset::operator|=bitset::operator^=bitset::operator~

bitset::operator<<=bitset::operator>>=bitset::operator<<bitset::operator>>

bitset::set

bitset::reset

bitset::flip

Conversions

bitset::to_string

bitset::to_ulong

bitset::to_ullong (C++11)

Non-member functions

operator&operator|operator^

operator<<operator>>

Helper classes

std::hash (C++11)

std::size_t count() const;

Returns the number of bits that are set to true.

Parameters

(none)

Return value

number of bits that are set to true.

Exceptions

(none)	(until C++11)
noexcept specification: noexcept	(since C++11)

Example

Run this code

#include <iostream>
#include <bitset>

int main()
{
    std::bitset<8> b("00010010");
    std::cout << "initial value: " << b << '\n';

    // find the first unset bit
    size_t idx = 0;
    while (idx < b.size() && b.test(idx)) ++idx;

    // continue setting bits until half the bitset is filled
    while (idx < b.size() && b.count() < b.size()/2) {
        b.set(idx);
        std::cout << "setting bit " << idx << ": " << b << '\n';
        while (idx < b.size() && b.test(idx)) ++idx;
    }

}

Output:

initial value: 00010010
setting bit 0: 00010011
setting bit 2: 00010111

See also

size	returns the size number of bits that the bitset can hold (public member function)