bitset::reference

A proxy class that provides references to bits contained in a bitset that is used to access and manipulate the individual bits as a helper class for the operator[] of class bitset.

class reference {
   friend class bitset<N>;
   public:
      reference& operator=(
         bool _Val
      );
      reference& operator=(
         const reference& _Bitref
      );
      bool operator~( ) const;
      operator bool( ) const;
      reference& flip( );
};

Parameters

• _Val
  The value of the object of type bool to be assigned to a bit in a bitset.

• _Bitref
  A reference of the form x [ i ] to the bit at position i in bitset x.

Return Value

A reference to the bit in the bitset specified by the argument position for the first, second, and fifth member functions of class reference, and true or false, to reflect the value of the modified bit in the bitset for the third and fourth member functions of class reference.

Remarks

The class reference exists only as a helper class for the bitset operator[]. The member class describes an object that can access an individual bit within a bitset. Let b be an object of type bool, x and y objects of type bitset<N>, and i and j valid positions within such an object. The notation x [i] references the bit at position i in bitset x. The member functions of class reference provide, in order, the following operations:

Operation	Definition
x[i] = b	Stores bool value b at bit position i in bitset x.
x[i] = y[j]	Stores the value of the bit y[j] at bit position i in bitset x.
b = ~x[i]	Stores the flipped value of the bit x[i] in bool b.
b = x[i]	Stores the value of the bit x[i] in bool b.
x[i].flip( )	Stores the flipped value of the bit x[i] back at bit position i in x.

Example

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

int main( )
{
   using namespace std;

   bitset<5> b1 ( 2 );
   bitset<5> b2 ( 6 );
   cout << "The initialized bitset<5> b1( 2 ) is: ( "<< b1 << " )."
        << endl;
   cout << "The initialized bitset<5> b2( 6 ) is: ( "<< b2 << " )."
        << endl;

   // Example of x [i] = b storing bool b at bit position i
   // in bitset x
   b1[ 0 ] = true;
   cout << "The bitset<5> b1 with the bit at position 0 set to 1"
        << " is: ( "<< b1 << " )" << endl;
   
   // Example of x [i] = y [j] storing the bool value of the
   // bit at position j in bitset y at bit position i in bitset x
   b2 [4] = b1 [0];      // b1 [0] = true
   cout << "The bitset<5> b2 with the bit at position 4 set to the "
        << "value\n of the bit at position 0 of the bit in "
        << "bitset<5> b1 is: ( "<<  b2  << " )" << endl;

   // Example of b = ~x [i] flipping the value of the bit at
   // position i of bitset x and storing the value in an 
   // object b of type bool
   bool b = ~b2 [4];      // b2 [4] = false
   if ( b )
      cout << "The value of the object b = ~b2 [4] "
           << "of type bool is true." << endl;
   else
      cout << "The value of the object b = ~b2 [4] "
           << "of type bool is false." << endl;
   
   // Example of b = x [i] storing the value of the bit at
   // position i of bitset x in the object b of type bool
   b = b2 [4];
   if ( b )
      cout << "The value of the object b = b2 [4] "
           << "of type bool is true." << endl;
   else
      cout << "The value of the object b = b2 [4] "
           << "of type bool is false." << endl;

   // Example of x [i] . flip ( ) toggling the value of the bit at
   // position i of bitset x
   cout << "Before flipping the value of the bit at position 4 in "
        << "bitset b2,\n it is ( "<<  b2  << " )." << endl;
   b2 [4].flip( );
   cout << "After flipping the value of the bit at position 4 in "
        << "bitset b2,\n it becomes ( "<<  b2  << " )." << endl;
   bool c;
   c = b2 [4].flip( );
   cout << "After a second toggle, the value of the position 4"
        << " bit in b2 is now: " << c << ".";
}

The initialized bitset<5> b1( 2 ) is: ( 00010 ).
The initialized bitset<5> b2( 6 ) is: ( 00110 ).
The bitset<5> b1 with the bit at position 0 set to 1 is: ( 00011 )
The bitset<5> b2 with the bit at position 4 set to the value
 of the bit at position 0 of the bit in bitset<5> b1 is: ( 10110 )
The value of the object b = ~b2 [4] of type bool is false.
The value of the object b = b2 [4] of type bool is true.
Before flipping the value of the bit at position 4 in bitset b2,
 it is ( 10110 ).
After flipping the value of the bit at position 4 in bitset b2,
 it becomes ( 00110 ).
After a second toggle, the value of the position 4 bit in b2 is now: 1.

Requirements

Header: <bitset>

Namespace: std

See Also

Concepts

bitset Class

bitset Members

Thread Safety in the Standard C++ Library