bitset::bitset

  • Article

Constructs an object of class bitset<N> and initializes the bits to zero, or to some specified value, or to values obtained from characters in a string.

bitset( );
bitset(
   unsigned long long _Val
);
explicit bitset(
   const char * _CStr
); 
template< 
  class CharType, 
  class Traits, 
  class Allocator 
>
  explicit bitset(
    const basic_string< CharType, Traits, Allocator >& _Str,
    typename basic_string< 
      CharType, Traits, Allocator >::size_type _Pos = 0
  );
template<
  class CharType,
  class Traits,
  class Allocator 
>
 explicit bitset(
  const basic_string< CharType, Traits, Allocator >& _Str,
  typename basic_string<
    CharType, Traits, Allocator >::size_type _Pos,
  typename basic_string< 
    CharType, Traits, Allocator >::size_type _Count,
  CharType _Zero = CharType (’0’), 
  CharType _One  = CharType (’1’)
);

Parameters

  • _Val
    The unsigned integer whose base two representation is used to initialize the bits in the bitset being constructed.

  • _Str
    The string of zeros and ones used to initialize the bitset bit values.

  • _CStr
    A C-style string of zeros and ones used to initialize the bitset bit values.

  • _Pos
    The position of the character in the string, counting from left to right and starting with zero, used to initialize the first bit in the bitset.

  • _Count
    The number of characters in the string that is used to provide initial values for the bits in the bitset.

  • _Zero
    The character that is used to represent a zero. The default is '0'.

  • _One
    The character that is used to represent a one. The default is '1'.

Remarks

Three constructors can be used to construct obects of class bitset<N>:

  • The first constructor accepts no parameters, constructs an object of class bitset<N> and initializes all N bits to a default value of zero.

  • The second constructor constructs an object of class bitset<N> and initializes the bits by using the single unsigned long long parameter.

  • The third constructor constructs an object of class bitset<N>, initializing the N bits to values that correspond to the characters provided in a c-style character string of zeros and ones. You call the constructor without casting the string into a string type: bitset<5> b5("01011");

There are also two constructor templates provided:

  • The first constructor template constructs an object of class bitset<N> and initializes bits from the characters provided in a string of zeros and ones. If any characters of the string are other than 0 or 1, the constructor throws an object of class invalid argument. If the position specified (_Pos) is beyond the length of the string, then the constructor throws an object of class out_of_range. The constructor sets only those bits at position j in the bitset for which the character in the string at position _Pos + j is 1. By default, _Pos is 0.

  • The second constructor template is similar to the first, but includes an additional parameter (_Count) that is used to specify the number of bits to initialize. It also has two optional parameters, _Zero and _One, which indicate what character in _Str is to be interpreted to mean a 0 bit and a 1 bit, respectively.

Example

// bitset_bitset.cpp
// compile with: /EHsc
#include <bitset>
#include <iostream>

int main( )
{
   // Using the default constructor
   using namespace std;
   bitset<2> b0;
   cout << "The set of bits in bitset<2> b0 is: ( "
        << b0 << " )." << endl;

   // Using the second member function
   bitset<5> b1 ( 6 );
   cout << "The set of bits in bitset<5> b1( 6 ) is: ( "
        << b1 << " )." << endl;

   // The template parameter N can be an expresssion
   bitset< 2 * sizeof ( int ) > b2;
   cout << "The set of bits in bitset<2 * sizeof ( int ) > b2 is: ( "
        << b2 << " )." << endl;

   // The base two representation will be truncated
   // if its length exceeds the size of the bitset
   bitset<3> b3 ( 6 );
   cout << "The set of bits in bitset<3> b3( 6 ) is ( "
        << b3 << " )." << endl;

   // Using a c-style string to initialize the bitset
    bitset<7> b3andahalf ( "1001001" );
    cout << "The set of bits in bitset<7> b3andahalf ( \"1001001\" )"
         << " is ( " << b3andahalf << " )." << endl; 

   // Using the fifth member function with the first parameter
   string bitval4 ( "10011" );
   bitset<5> b4 ( bitval4 );
   cout << "The set of bits in bitset<5> b4( bitval4 ) is ( "
        << b4 << " )." << endl;

   // Only part of the string may be used for initialization

   // Starting at position 3 for a length of 6 (100110)
   string bitval5 ("11110011011");
   bitset<6> b5 ( bitval5, 3, 6 );
   cout << "The set of bits in bitset<11> b5( bitval, 3, 6 ) is ( "
        << b5 << " )." << endl;

   // The bits not initialized with part of the string
   // will default to zero
   bitset<11> b6 ( bitval5, 3, 5 );
   cout << "The set of bits in bitset<11> b6( bitval5, 3, 5 ) is ( "
        << b6 << " )." << endl;

   // Starting at position 2 and continue to the end of the string
   bitset<9> b7 ( bitval5, 2 );
   cout << "The set of bits in bitset<9> b7( bitval, 2 ) is ( "
        << b7 << " )." << endl;
}

The set of bits in bitset<2> b0 is: ( 00 ).
The set of bits in bitset<5> b1( 6 ) is: ( 00110 ).
The set of bits in bitset<2 * sizeof ( int ) > b2 is: ( 00000000 ).
The set of bits in bitset<3> b3( 6 ) is ( 110 ).
The set of bits in bitset<5> b4( bitval4 ) is ( 10011 ).
The set of bits in bitset<11> b5( bitval, 3, 6 ) is ( 100110 ).
The set of bits in bitset<11> b6( bitval5, 3, 5 ) is ( 00000010011 ).
The set of bits in bitset<9> b7( bitval, 2 ) is ( 110011011 ).

Requirements

Header: <bitset>

Namespace: std

See Also

Reference

bitset Class