NAME¶

std::bitset::bitset - std::bitset::bitset

Synopsis¶

bitset(); (until
C++11)
constexpr bitset() noexcept; (since
C++11)
bitset( unsigned long val ); (until
C++11)
constexpr bitset( unsigned long long val ) (since
noexcept; C++11)
template< class CharT, class Traits, class Alloc
>

explicit bitset( const
std::basic_string<CharT,Traits,Alloc>& str,
typename (until
std::basic_string<CharT,Traits,Alloc>::size_type C++11)
pos = 0,
typename
std::basic_string<CharT,Traits,Alloc>::size_type

n = std::basic_string<CharT,Traits,Alloc>::npos
);
template< class CharT, class Traits, class Alloc (1)
>
(2)
explicit bitset( const
std::basic_string<CharT,Traits,Alloc>& str, (3) (since
typename C++11)
std::basic_string<CharT,Traits,Alloc>::size_type (constexpr
pos = 0, since
typename C++23)
std::basic_string<CharT,Traits,Alloc>::size_type
n = std::basic_string<CharT,Traits,Alloc>::npos,
CharT zero = CharT('0'),

CharT one = CharT('1') );
template< class CharT >
(since
explicit bitset( const CharT* str, C++11)
typename std::basic_string<CharT>::size_type (4) (constexpr
n = std::basic_string<CharT>::npos, since
CharT zero = CharT('0'), C++23)

CharT one = CharT('1') );

Constructs a new bitset from one of several optional data sources:

1) Default constructor. Constructs a bitset with all bits set to zero.
2) Constructs a bitset, initializing the first (rightmost, least significant) M bit
positions to the corresponding bit values of val, where M is the smaller of the
number of bits in an unsigned long long and the number of bits N in the bitset being
constructed. If M is less than N (the bitset is longer than
32
(until C++11)
64
(since C++11) bits, for typical implementations of unsigned
long
(since C++11)long), the remaining bit positions are initialized to zeroes.
3) Constructs a bitset using the characters in the std::basic_string str. An
optional starting position pos and length n can be provided, as well as characters
denoting alternate values for set (one) and unset (zero) bits. Traits::eq() is used
to compare the character values.
The effective length of the initializing string is min(n, str.size() - pos).
If pos > str.size(), this constructor throws std::out_of_range. If any characters
examined in str are not zero or one, it throws std::invalid_argument.
4) Similar to (3), but uses a CharT* instead of a std::basic_string. Equivalent to

bitset(n == basic_string<CharT>::npos
? basic_string<CharT>(str)
: basic_string<CharT>(str, n), 0, n, zero, one)

Parameters¶

val - number used to initialize the bitset
str - string used to initialize the bitset
pos - a starting offset into str
n - number of characters to use from str
one - alternate character for set bits in str
zero - alternate character for unset bits in str

Exceptions¶

3) std::out_of_range if pos > str.size(), std::invalid_argument if any character is
not one or zero
4) std::invalid_argument if any character is not one or zero

Example¶

// Run this code

#include <bitset>
#include <string>
#include <iostream>
#include <climits>

int main()
{
// empty constructor
std::bitset<8> b1; // [0,0,0,0,0,0,0,0]

// unsigned long long constructor
std::bitset<8> b2(42); // [0,0,1,0,1,0,1,0]
std::bitset<70> bl(ULLONG_MAX); // [0,0,0,0,0,0,1,1,1,...,1,1,1] in C++11
std::bitset<8> bs(0xfff0); // [1,1,1,1,0,0,0,0]

// string constructor
std::string bit_string = "110010";
std::bitset<8> b3(bit_string); // [0,0,1,1,0,0,1,0]
std::bitset<8> b4(bit_string, 2); // [0,0,0,0,0,0,1,0]
std::bitset<8> b5(bit_string, 2, 3); // [0,0,0,0,0,0,0,1]

// string constructor using custom zero/one digits
std::string alpha_bit_string = "aBaaBBaB";
std::bitset<8> b6(alpha_bit_string, 0, alpha_bit_string.size(),
'a', 'B'); // [0,1,0,0,1,1,0,1]

// char* constructor using custom digits
std::bitset<8> b7("XXXXYYYY", 8, 'X', 'Y'); // [0,0,0,0,1,1,1,1]

std::cout << "b1: " << b1 << "\nb2: " << b2 << "\nbl: " << bl
<< "\nbs: " << bs << "\nb3: " << b3 << "\nb4: " << b4
<< "\nb5: " << b5 << "\nb6: " << b6 << "\nb7: " << b7 << '\n';
}

Possible output:¶

b1: 00000000
b2: 00101010
bl: 0000001111111111111111111111111111111111111111111111111111111111111111
bs: 11110000
b3: 00110010
b4: 00000010
b5: 00000001
b6: 01001101
b7: 00001111

See also¶

set sets bits to true or given value
(public member function)
reset sets bits to false
(public member function)