std::bitset(3)

NAME
std::bitset - The bitset class represents a fixed-size sequence of bits.

SYNOPSIS

Inherits std::_Base_bitset< _GLIBCPP_BITSET_WORDS(_Nb)>.

  Public Member Functions
bitset ()
All bits set to zero.
bitset (unsigned long __val)
Initial bits bitwise-copied from a single word (others set to zero).
template<class _CharT, class _Traits, class _Alloc> bitset (const basic_string< _CharT, _Traits, _Alloc > &__s, size_t __pos=0)
Use a subset of a string.
template<class _CharT, class _Traits, class _Alloc> bitset (const basic_string< _CharT, _Traits, _Alloc > &__s, size_t __pos, size_t __n)
Use a subset of a string.
bitset< _Nb > & set ()
Sets every bit to true.
bitset< _Nb > & set (size_t __pos, bool __val=true)
Sets a given bit to a particular value.
bitset< _Nb > & reset ()
Sets every bit to false.
bitset< _Nb > & reset (size_t __pos)
Sets a given bit to false.
bitset< _Nb > & flip ()
Toggles every bit to its opposite value.
bitset< _Nb > & flip (size_t __pos)
Toggles a given bit to its opposite value.
bitset< _Nb > operator~ () const
See the no-argument flip().
unsigned long to_ulong () const
Retuns a numerical interpretation of the bitset.
template<class _CharT, class _Traits, class _Alloc> basic_string< _CharT, _Traits, _Alloc > to_string () const
Retuns a character interpretation of the bitset.
size_t count () const
Returns the number of bits which are set.
size_t size () const
Returns the total number of bits.
bool test (size_t __pos) const
Tests the value of a bit.
bool any () const
Tests whether any of the bits are on.
bool none () const
Tests whether any of the bits are on.
size_t _Find_first () const
Finds the index of the first 'on' bit.
size_t _Find_next (size_t __prev) const
Finds the index of the next 'on' bit after prev.

bitset< _Nb > & operator &= (const bitset< _Nb > &__rhs)
Operations on bitsets.
bitset< _Nb > & operator|= (const bitset< _Nb > &__rhs)
Operations on bitsets.
bitset< _Nb > & operator^= (const bitset< _Nb > &__rhs)
Operations on bitsets.

bitset< _Nb > & operator<<= (size_t __pos)
Operations on bitsets.
bitset< _Nb > & operator>>= (size_t __pos)
Operations on bitsets.

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

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

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

bitset< _Nb > operator<< (size_t __pos) const
Self-explanatory.
bitset< _Nb > operator>> (size_t __pos) const
Self-explanatory.

  Private Attributes
_WordT _M_w [_Nw]
0 is the least significant word.

Detailed Description

  template<size_t _Nb> 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 - Nb%B 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
              << 'index 3 in the bitset is ' << b[3] << endl;
     }

Also see http://gcc.gnu.org/onlinedocs/libstdc++/ext/sgiexts.html#ch23 for a description of extensions.

Definition at line 639 of file bitset.

Constructor & Destructor Documentation

  template<size_t _Nb> std::bitset< _Nb >::bitset () [inline]

All bits set to zero.

Definition at line 727 of file bitset.

  template<size_t _Nb> std::bitset< _Nb >::bitset (unsigned long __val) [inline]

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

Definition at line 730 of file bitset.

  template<size_t _Nb> template<class _CharT, class _Traits, class _Alloc> std::bitset< _Nb >::bitset (const basic_string< _CharT, _Traits, _Alloc > & __s, size_t __pos = 0) [inline, explicit]

Use a subset of a string.Parameters:
    s A string of '0' and '1' characters.
    pos Index of the first character in s to use; defaults to zero.

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'.

Definition at line 743 of file bitset.

References std::basic_string< _CharT, _Traits, _Alloc >::size().

  template<size_t _Nb> template<class _CharT, class _Traits, class _Alloc> std::bitset< _Nb >::bitset (const basic_string< _CharT, _Traits, _Alloc > & __s, size_t __pos, size_t __n) [inline]

Use a subset of a string.Parameters:
    s A string of '0' and '1' characters.
    pos Index of the first character in s to use.
    n The number of characters to copy.

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'.

Definition at line 763 of file bitset.

References std::basic_string< _CharT, _Traits, _Alloc >::size().

Member Function Documentation

  template<size_t _Nb> bool std::bitset< _Nb >::any () const [inline]

Tests whether any of the bits are on.Returns:
    True if at least one bit is set.

Definition at line 1064 of file bitset.

  template<size_t _Nb> size_t std::bitset< _Nb >::count () const [inline]

Returns the number of bits which are set.

Definition at line 1028 of file bitset.

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::flip (size_t __pos) [inline]

Toggles a given bit to its opposite value.Parameters:
    pos The index of the bit.

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

Definition at line 949 of file bitset.

References std::bitset< _Nb >::_Unchecked_flip().

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::flip () [inline]

Toggles every bit to its opposite value.

Definition at line 936 of file bitset.

  template<size_t _Nb> bool std::bitset< _Nb >::none () const [inline]

Tests whether any of the bits are on.Returns:
    True if none of the bits are set.

Definition at line 1071 of file bitset.

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::operator &= (const bitset< _Nb > & __rhs) [inline]

Operations on bitsets.Parameters:
    rhs A same-sized bitset.

These should be self-explanatory.

Definition at line 781 of file bitset.

  template<size_t _Nb> bool std::bitset< _Nb >::operator!= (const bitset< _Nb > & __rhs) const [inline]

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

Definition at line 1041 of file bitset.

  template<size_t _Nb> bitset<_Nb> std::bitset< _Nb >::operator<< (size_t __pos) const [inline]

Self-explanatory.

Definition at line 1076 of file bitset.

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::operator<<= (size_t __pos) [inline]

Operations on bitsets.Parameters:
    pos The number of places to shift.

These should be self-explanatory.

Definition at line 810 of file bitset.

  template<size_t _Nb> bool std::bitset< _Nb >::operator== (const bitset< _Nb > & __rhs) const [inline]

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

Definition at line 1037 of file bitset.

  template<size_t _Nb> bitset<_Nb> std::bitset< _Nb >::operator>> (size_t __pos) const [inline]

Self-explanatory.

Definition at line 1080 of file bitset.

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::operator>>= (size_t __pos) [inline]

Operations on bitsets.Parameters:
    pos The number of places to shift.

These should be self-explanatory.

Definition at line 823 of file bitset.

  template<size_t _Nb> bool std::bitset< _Nb >::operator[] (size_t __pos) const [inline]

Array-indexing support.Parameters:
    pos Index into the bitset.

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.

Definition at line 981 of file bitset.

References std::bitset< _Nb >::_Unchecked_test().

  template<size_t _Nb> reference std::bitset< _Nb >::operator[] (size_t __pos) [inline]

Array-indexing support.Parameters:
    pos Index into the bitset.

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.

Definition at line 978 of file bitset.

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::operator^= (const bitset< _Nb > & __rhs) [inline]

Operations on bitsets.Parameters:
    rhs A same-sized bitset.

These should be self-explanatory.

Definition at line 795 of file bitset.

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::operator|= (const bitset< _Nb > & __rhs) [inline]

Operations on bitsets.Parameters:
    rhs A same-sized bitset.

These should be self-explanatory.

Definition at line 788 of file bitset.

  template<size_t _Nb> bitset<_Nb> std::bitset< _Nb >::operator~ () const [inline]

See the no-argument flip().

Definition at line 958 of file bitset.

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::reset (size_t __pos) [inline]

Sets a given bit to false.Parameters:
    pos The index of the bit.

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

Same as writing set(pos,false).

Definition at line 925 of file bitset.

References std::bitset< _Nb >::_Unchecked_reset().

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::reset () [inline]

Sets every bit to false.

Definition at line 911 of file bitset.

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::set (size_t __pos, bool __val = true) [inline]

Sets a given bit to a particular value.Parameters:
    pos The index of the bit.
    val Either true or false, defaults to true.

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

Definition at line 900 of file bitset.

References std::bitset< _Nb >::_Unchecked_set().

  template<size_t _Nb> bitset<_Nb>& std::bitset< _Nb >::set () [inline]

Sets every bit to true.

Definition at line 886 of file bitset.

  template<size_t _Nb> size_t std::bitset< _Nb >::size () const [inline]

Returns the total number of bits.

Definition at line 1032 of file bitset.

  template<size_t _Nb> bool std::bitset< _Nb >::test (size_t __pos) const [inline]

Tests the value of a bit.Parameters:
    pos The index of a bit.

Returns:
    The value at pos.

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

Definition at line 1052 of file bitset.

References std::bitset< _Nb >::_Unchecked_test().

  template<size_t _Nb> template<class _CharT, class _Traits, class _Alloc> basic_string<_CharT, _Traits, _Alloc> std::bitset< _Nb >::to_string () const [inline]

Retuns 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).

Also note that you must specify the string's template parameters explicitly. Given a bitset bs and a string :

     s = bs.to_string<char,char_traits<char>,allocator<char> >();

Definition at line 1009 of file bitset.

  template<size_t _Nb> unsigned long std::bitset< _Nb >::to_ulong () const [inline]

Retuns 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.

Definition at line 991 of file bitset.

Member Data Documentation

  _WordT std::_Base_bitset< _Nw >::_M_w[_Nw] [inherited]

0 is the least significant word.

Definition at line 85 of file bitset.

Author

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