std::bitset

 

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std::bitset

Member types
bitset::reference
Member functions
bitset::bitset
bitset::operator==bitset::operator!= (until C++20)
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)

 

Defined in header <bitset>
template< std::size_t N > class bitset;

The class template bitset represents a fixed-size sequence of N bits. Bitsets can be manipulated by standard logic operators and converted to and from strings and integers. For the purpose of the string representation and of naming directions for shift operations, the sequence is thought of as having its lowest indexed elements at the right, as in the binary representation of integers.

bitset meets the requirements of CopyConstructible and CopyAssignable.

All member functions of std::bitset are constexpr: it is possible to create and use std::bitset objects in the evaluation of a constant expression.

(since C++23)

Template parameters

N

-

the number of bits to allocate storage for

Member types

reference

proxy class representing a reference to a bit (class)

Member functions

(constructor)	constructs the bitset (public member function)
operator==operator!= (removed in C++20)	compares the contents (public member function)
Element access
operator[]	accesses specific bit (public member function)
test	accesses specific bit (public member function)
allanynone	checks if all, any or none of the bits are set to true (public member function)
count	returns the number of bits set to true (public member function)
Capacity
size	returns the number of bits that the bitset holds (public member function)
Modifiers
operator&=operator|=operator^=operator~	performs binary AND, OR, XOR and NOT (public member function)
operator<<=operator>>=operator<<operator>>	performs binary shift left and shift right (public member function)
set	sets bits to true or given value (public member function)
reset	sets bits to false (public member function)
flip	toggles the values of bits (public member function)
Conversions
to_string	returns a string representation of the data (public member function)
to_ulong	returns an unsigned long integer representation of the data (public member function)
to_ullong (C++11)	returns an unsigned long long integer representation of the data (public member function)

Non-member functions

operator&operator|operator^	performs binary logic operations on bitsets (function template)
operator<<operator>>	performs stream input and output of bitsets (function template)

Helper classes

std::hash<std::bitset> (C++11)

hash support for std::bitset (class template specialization)

Notes

If the size of a bit-set is not known at compile time, or it is necessary to change its size at run-time, the dynamic types such as std::vector<bool> or boost::dynamic_bitset<> may be used instead.

Feature-test macro	Value	Std	Feature
__cpp_lib_constexpr_bitset	202207L	(C++23)	A more constexpr std::bitset
__cpp_lib_bitset	202306L	(C++26)	Interfacing std::bitset with std::string_view

Example

Run this code

#include <bitset>
#include <cassert>
#include <cstddef>
#include <iostream>
 
int main()
{
    typedef std::size_t length_t, position_t; // the hints
 
    // constructors:
    constexpr std::bitset<4> b1;
    constexpr std::bitset<4> b2{0xA}; // == 0B1010
    std::bitset<4> b3{"0011"}; // can also be constexpr since C++23
    std::bitset<8> b4{"ABBA", length_t(4), /*0:*/'A', /*1:*/'B'}; // == 0B0000'0110
 
    // bitsets can be printed out to a stream:
    std::cout << "b1:" << b1 << "; b2:" << b2 << "; b3:" << b3 << "; b4:" << b4 << '\n';
 
    // bitset supports bitwise operations:
    b3 |= 0b0100; assert(b3 == 0b0111);
    b3 &= 0b0011; assert(b3 == 0b0011);
    b3 ^= std::bitset<4>{0b1100}; assert(b3 == 0b1111);
 
    // operations on the whole set:
    b3.reset(); assert(b3 == 0);
    b3.set(); assert(b3 == 0b1111);
    assert(b3.all() && b3.any() && !b3.none());
    b3.flip(); assert(b3 == 0);
 
    // operations on individual bits:
    b3.set(position_t(1), true); assert(b3 == 0b0010);
    b3.set(position_t(1), false); assert(b3 == 0);
    b3.flip(position_t(2)); assert(b3 == 0b0100);
    b3.reset(position_t(2)); assert(b3 == 0);
 
    // subscript operator[] is supported:
    b3[2] = true; assert(true == b3[2]);
 
    // other operations:
    assert(b3.count() == 1);
    assert(b3.size() == 4);
    assert(b3.to_ullong() == 0b0100ULL);
    assert(b3.to_string() == "0100");
}

Output:

b1:0000; b2:1010; b3:0011; b4:00000110

See also

vector<bool>	space-efficient dynamic bitset (class template specialization)
Bit manipulation (C++20)	utilities to access, manipulate, and process individual bits and bit sequences