std::bitset - Man Page

class reference

constexpr bitset () noexcept
All bits set to zero.
template<typename _CharT > constexpr bitset (const _CharT *__str, typename __bitset::__string< _CharT >::size_type __n=__bitset::__string< _CharT >::npos, _CharT __zero=_CharT('0'), _CharT __one=_CharT('1'))
template<class _CharT , class _Traits , class _Alloc > constexpr bitset (const std::basic_string< _CharT, _Traits, _Alloc > &__s, size_t __position, size_t __n)
template<class _CharT , class _Traits , class _Alloc > constexpr bitset (const std::basic_string< _CharT, _Traits, _Alloc > &__s, size_t __position, size_t __n, _CharT __zero, _CharT __one=_CharT('1'))
template<class _CharT , class _Traits , class _Alloc > constexpr bitset (const std::basic_string< _CharT, _Traits, _Alloc > &__s, size_t __position=0)
constexpr bitset (unsigned long long __val) noexcept
Initial bits bitwise-copied from a single word (others set to zero).
constexpr size_t _Find_first () const noexcept
Finds the index of the first 'on' bit.
constexpr size_t _Find_next (size_t __prev) const noexcept
Finds the index of the next 'on' bit after prev.
constexpr bool all () const noexcept
Tests whether all the bits are on.
constexpr bool any () const noexcept
Tests whether any of the bits are on.
constexpr size_t count () const noexcept
Returns the number of bits which are set.
constexpr bitset< _Nb > & flip () noexcept
Toggles every bit to its opposite value.
constexpr bitset< _Nb > & flip (size_t __position)
Toggles a given bit to its opposite value.
constexpr bool none () const noexcept
Tests whether any of the bits are on.
constexpr bitset< _Nb > operator~ () const noexcept
See the no-argument flip().
constexpr bitset< _Nb > & reset () noexcept
Sets every bit to false.
constexpr bitset< _Nb > & reset (size_t __position)
Sets a given bit to false.
constexpr bitset< _Nb > & set () noexcept
Sets every bit to true.
constexpr bitset< _Nb > & set (size_t __position, bool __val=true)
Sets a given bit to a particular value.
constexpr size_t size () const noexcept
Returns the total number of bits.
constexpr bool test (size_t __position) const
Tests the value of a bit.
template<class _CharT , class _Traits , class _Alloc > constexpr std::basic_string< _CharT, _Traits, _Alloc > to_string () const
Returns a character interpretation of the bitset.
template<class _CharT , class _Traits > constexpr std::basic_string< _CharT, _Traits, std::allocator< _CharT > > to_string () const
template<class _CharT > constexpr std::basic_string< _CharT, std::char_traits< _CharT >, std::allocator< _CharT > > to_string () const
constexpr std::basic_string< char, std::char_traits< char >, std::allocator< char > > to_string () const
template<class _CharT , class _Traits , class _Alloc > constexpr std::basic_string< _CharT, _Traits, _Alloc > to_string (_CharT __zero, _CharT __one=_CharT('1')) const
template<class _CharT , class _Traits > constexpr std::basic_string< _CharT, _Traits, std::allocator< _CharT > > to_string (_CharT __zero, _CharT __one=_CharT('1')) const
template<class _CharT > constexpr std::basic_string< _CharT, std::char_traits< _CharT >, std::allocator< _CharT > > to_string (_CharT __zero, _CharT __one=_CharT('1')) const
constexpr std::basic_string< char, std::char_traits< char >, std::allocator< char > > to_string (char __zero, char __one='1') const
constexpr unsigned long long to_ullong () const
constexpr unsigned long to_ulong () const
Returns a numerical interpretation of the bitset.

constexpr bitset< _Nb > & operator&= (const bitset< _Nb > &__rhs) noexcept
constexpr bitset< _Nb > & operator|= (const bitset< _Nb > &__rhs) noexcept
constexpr bitset< _Nb > & operator^= (const bitset< _Nb > &__rhs) noexcept

constexpr bitset< _Nb > & operator<<= (size_t __position) noexcept
constexpr bitset< _Nb > & operator>>= (size_t __position) noexcept

constexpr bitset< _Nb > & _Unchecked_set (size_t __pos) noexcept
constexpr bitset< _Nb > & _Unchecked_set (size_t __pos, int __val) noexcept
constexpr bitset< _Nb > & _Unchecked_reset (size_t __pos) noexcept
constexpr bitset< _Nb > & _Unchecked_flip (size_t __pos) noexcept
constexpr bool _Unchecked_test (size_t __pos) const noexcept

constexpr reference operator[] (size_t __position)
Array-indexing support.
constexpr bool operator[] (size_t __position) const
Array-indexing support.

constexpr bool operator== (const bitset< _Nb > &__rhs) const noexcept
These comparisons for equality/inequality are, well, bitwise.

constexpr bitset< _Nb > operator<< (size_t __position) const noexcept
Self-explanatory.
constexpr bitset< _Nb > operator>> (size_t __position) const noexcept
Self-explanatory.

template<class _CharT , class _Traits , size_t _Nb2> std::basic_ostream< _CharT, _Traits > & operator<< (std::basic_ostream< _CharT, _Traits > &, const bitset< _Nb2 > &)
template<class _CharT , class _Traits , size_t _Nb2> std::basic_istream< _CharT, _Traits > & operator>> (std::basic_istream< _CharT, _Traits > &, bitset< _Nb2 > &)
class reference
struct std::hash< bitset >

class std::bitset< _Nb >"The bitset class represents a fixed-size sequence of bits.

(Note that bitset does not meet the formal requirements of a container. Mainly, it lacks iterators.)

The template argument, Nb, may be any non-negative number, specifying the number of bits (e.g., '0', '12', '1024*1024').

In the general unoptimized case, storage is allocated in word-sized blocks. Let B be the number of bits in a word, then (Nb+(B-1))/B words will be used for storage. B - NbB bits are unused. (They are the high-order bits in the highest word.) It is a class invariant that those unused bits are always zero.

If you think of bitset as a simple array of bits, be aware that your mental picture is reversed: a bitset behaves the same way as bits in integers do, with the bit at index 0 in the least significant / right-hand position, and the bit at index Nb-1 in the most significant / left-hand position. Thus, unlike other containers, a bitset's index counts from right to left, to put it very loosely.

This behavior is preserved when translating to and from strings. For example, the first line of the following program probably prints b('a') is 0001100001 on a modern ASCII system.

#include <bitset>
#include <iostream>
#include <sstream>

using namespace std;

int main()
{
    long         a = 'a';
    bitset<10>   b(a);

    cout << "b('a') is " << b << endl;

    ostringstream s;
    s << b;
    string  str = s.str();
    cout << "index 3 in the string is " << str[3] << " but\n"
         << "index 3 in the bitset is " << b[3] << endl;
}

Also see: https://gcc.gnu.org/onlinedocs/libstdc++/manual/ext_containers.html for a description of extensions.

Most of the actual code isn't contained in bitset<> itself, but in the base class _Base_bitset. The base class works with whole words, not with individual bits. This allows us to specialize _Base_bitset for the important special case where the bitset is only a single word.

Extra confusion can result due to the fact that the storage for _Base_bitset is a regular array, and is indexed as such. This is carefully encapsulated.

All bits set to zero.

Initial bits bitwise-copied from a single word (others set to zero).

Use a subset of a string.

Parameters

Exceptions

std::out_of_range If pos is bigger the size of __s.
std::invalid_argument If a character appears in the string which is neither 0 nor 1.

Use a subset of a string.

Parameters

Exceptions

std::out_of_range If __position is bigger the size of __s.
std::invalid_argument If a character appears in the string which is neither 0 nor 1.

Construct from a character array.

Parameters

Exceptions

std::invalid_argument If a character appears in the string which is neither __zero nor __one.

Tests whether all the bits are on.

Returns

True if all the bits are set.

Tests whether any of the bits are on.

Returns

True if at least one bit is set.

Returns the number of bits which are set.

Toggles every bit to its opposite value.

Toggles a given bit to its opposite value.

Parameters

Exceptions

std::out_of_range If pos is bigger the size of the set.

Tests whether any of the bits are on.

Returns

True if none of the bits are set.

Operations on bitsets.

Parameters

These should be self-explanatory.

Self-explanatory.

Operations on bitsets.

Parameters

These should be self-explanatory.

These comparisons for equality/inequality are, well, bitwise.

Self-explanatory.

Operations on bitsets.

Parameters

These should be self-explanatory.

Array-indexing support.

Parameters

Returns

A bool for a const bitset. For non-const bitsets, an instance of the reference proxy class.

Note

These operators do no range checking and throw no exceptions, as required by DR 11 to the standard.

_GLIBCXX_RESOLVE_LIB_DEFECTS Note that this implementation already resolves DR 11 (items 1 and 2), but does not do the range-checking required by that DR's resolution. -pme The DR has since been changed: range-checking is a precondition (users' responsibility), and these functions must not throw. -pme

Array-indexing support.

Parameters

Returns

A bool for a const bitset. For non-const bitsets, an instance of the reference proxy class.

Note

These operators do no range checking and throw no exceptions, as required by DR 11 to the standard.

_GLIBCXX_RESOLVE_LIB_DEFECTS Note that this implementation already resolves DR 11 (items 1 and 2), but does not do the range-checking required by that DR's resolution. -pme The DR has since been changed: range-checking is a precondition (users' responsibility), and these functions must not throw. -pme

Operations on bitsets.

Parameters

These should be self-explanatory.

Operations on bitsets.

Parameters

These should be self-explanatory.

See the no-argument flip().

Sets every bit to false.

Sets a given bit to false.

Parameters

Exceptions

std::out_of_range If pos is bigger the size of the set.

Same as writing set(pos,false).

Sets every bit to true.

Sets a given bit to a particular value.

Parameters

Exceptions

std::out_of_range If pos is bigger the size of the set.

Returns the total number of bits.

Tests the value of a bit.

Parameters

Returns

The value at pos.

Exceptions

std::out_of_range If pos is bigger the size of the set.

Returns a character interpretation of the bitset.

Returns

The string equivalent of the bits.

Note the ordering of the bits: decreasing character positions correspond to increasing bit positions (see the main class notes for an example).

Returns a numerical interpretation of the bitset.

Returns

The integral equivalent of the bits.

Exceptions

std::overflow_error If there are too many bits to be represented in an unsigned long.