(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 http://gcc.gnu.org/onlinedocs/libstdc++/ext/sgiexts.html#ch23 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.
Definition at line 650 of file bitset.
std::bitset< _Nb >::bitset | ( | ) | [inline] |
std::bitset< _Nb >::bitset | ( | unsigned long | __val | ) | [inline] |
std::bitset< _Nb >::bitset | ( | const std::basic_string< _CharT, _Traits, _Alloc > & | __s, | |
size_t | __position = 0 | |||
) | [inline, explicit] |
Use a subset of a string.
s | A string of '0' and '1' characters. | |
position | Index of the first character in s to use; defaults to zero. |
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 759 of file bitset.
References __N, std::bitset< _Nb >::_M_copy_from_string(), and std::basic_string< _CharT, _Traits, _Alloc >::size().
std::bitset< _Nb >::bitset | ( | const std::basic_string< _CharT, _Traits, _Alloc > & | __s, | |
size_t | __position, | |||
size_t | __n | |||
) | [inline] |
Use a subset of a string.
s | A string of '0' and '1' characters. | |
position | Index of the first character in s to use. | |
n | The number of characters to copy. |
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 780 of file bitset.
References __N, std::bitset< _Nb >::_M_copy_from_string(), and std::basic_string< _CharT, _Traits, _Alloc >::size().
bool std::bitset< _Nb >::all | ( | ) | const [inline] |
Tests whether all the bits are on.
Definition at line 1104 of file bitset.
References std::_Base_bitset< _Nw >::_M_are_all_aux().
bool std::bitset< _Nb >::any | ( | ) | const [inline] |
Tests whether any of the bits are on.
Definition at line 1112 of file bitset.
References std::_Base_bitset< _Nw >::_M_is_any().
size_t std::bitset< _Nb >::count | ( | ) | const [inline] |
Returns the number of bits which are set.
Definition at line 1064 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_count().
bitset<_Nb>& std::bitset< _Nb >::flip | ( | size_t | __position | ) | [inline] |
Toggles a given bit to its opposite value.
position | The index of the bit. |
std::out_of_range | If pos is bigger the size of the set. |
Definition at line 965 of file bitset.
References __N, and std::bitset< _Nb >::_Unchecked_flip().
bitset<_Nb>& std::bitset< _Nb >::flip | ( | ) | [inline] |
Toggles every bit to its opposite value.
Definition at line 952 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_flip().
bool std::bitset< _Nb >::none | ( | ) | const [inline] |
Tests whether any of the bits are on.
Definition at line 1120 of file bitset.
References std::_Base_bitset< _Nw >::_M_is_any().
bitset<_Nb>& std::bitset< _Nb >::operator &= | ( | const bitset< _Nb > & | __rhs | ) | [inline] |
Operations on bitsets.
rhs | A same-sized bitset. |
Definition at line 799 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_and().
bitset<_Nb> std::bitset< _Nb >::operator<< | ( | size_t | __position | ) | const [inline] |
bitset<_Nb>& std::bitset< _Nb >::operator<<= | ( | size_t | __position | ) | [inline] |
Operations on bitsets.
position | The number of places to shift. |
Definition at line 828 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_left_shift(), and std::_Base_bitset< _Nw >::_M_do_reset().
bool std::bitset< _Nb >::operator== | ( | const bitset< _Nb > & | __rhs | ) | const [inline] |
These comparisons for equality/inequality are, well, bitwise.
Definition at line 1075 of file bitset.
References std::_Base_bitset< _Nw >::_M_is_equal().
bitset<_Nb> std::bitset< _Nb >::operator>> | ( | size_t | __position | ) | const [inline] |
bitset<_Nb>& std::bitset< _Nb >::operator>>= | ( | size_t | __position | ) | [inline] |
Operations on bitsets.
position | The number of places to shift. |
Definition at line 841 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_reset(), and std::_Base_bitset< _Nw >::_M_do_right_shift().
reference std::bitset< _Nb >::operator[] | ( | size_t | __position | ) | [inline] |
Array-indexing support.
position | Index into the bitset. |
Definition at line 993 of file bitset.
References std::bitset< _Nb >::reference.
bitset<_Nb>& std::bitset< _Nb >::operator^= | ( | const bitset< _Nb > & | __rhs | ) | [inline] |
Operations on bitsets.
rhs | A same-sized bitset. |
Definition at line 813 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_xor().
bitset<_Nb>& std::bitset< _Nb >::operator|= | ( | const bitset< _Nb > & | __rhs | ) | [inline] |
Operations on bitsets.
rhs | A same-sized bitset. |
Definition at line 806 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_or().
bitset<_Nb> std::bitset< _Nb >::operator~ | ( | ) | const [inline] |
bitset<_Nb>& std::bitset< _Nb >::reset | ( | size_t | __position | ) | [inline] |
Sets a given bit to false.
position | The index of the bit. |
std::out_of_range | If pos is bigger the size of the set. |
set(pos,false)
.
Definition at line 941 of file bitset.
References __N, and std::bitset< _Nb >::_Unchecked_reset().
bitset<_Nb>& std::bitset< _Nb >::reset | ( | ) | [inline] |
Sets every bit to false.
Definition at line 927 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_reset().
Referenced by std::bitset< _Nb >::_M_copy_from_string().
bitset<_Nb>& std::bitset< _Nb >::set | ( | size_t | __position, | |
bool | __val = true | |||
) | [inline] |
Sets a given bit to a particular value.
position | The index of the bit. | |
val | Either true or false, defaults to true. |
std::out_of_range | If pos is bigger the size of the set. |
Definition at line 916 of file bitset.
References __N, and std::bitset< _Nb >::_Unchecked_set().
bitset<_Nb>& std::bitset< _Nb >::set | ( | ) | [inline] |
Sets every bit to true.
Definition at line 902 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_set().
size_t std::bitset< _Nb >::size | ( | ) | const [inline] |
bool std::bitset< _Nb >::test | ( | size_t | __position | ) | const [inline] |
Tests the value of a bit.
position | The index of a bit. |
std::out_of_range | If pos is bigger the size of the set. |
Definition at line 1090 of file bitset.
References __N, and std::bitset< _Nb >::_Unchecked_test().
std::basic_string<_CharT, _Traits, _Alloc> std::bitset< _Nb >::to_string | ( | ) | const [inline] |
Returns a character interpretation of the bitset.
Definition at line 1021 of file bitset.
References std::bitset< _Nb >::_M_copy_to_string().
unsigned long std::bitset< _Nb >::to_ulong | ( | ) | const [inline] |
Returns a numerical interpretation of the bitset.
std::overflow_error | If there are too many bits to be represented in an unsigned long . |
Definition at line 1008 of file bitset.
References std::_Base_bitset< _Nw >::_M_do_to_ulong().