C++ Tutorial/bitset/bitset

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A bitset to hold 8-bits

#include <bitset>
#include <string>
#include <iostream>
int main ()
{
    using namespace std;
    // A bitset to hold 8-bits
    bitset <8> eightBits;
    cout << "Enter a 8-bit sequence: ";
    // Store user-supplied sequence into the bitset
    cin >> eightBits;
    cout << endl;
    return 0;
}

Create a copy of a bitset

#include <bitset>
#include <string>
#include <iostream>
int main ()
{
    using namespace std;
    // A bitset to hold 8-bits
    bitset <8> eightBits;
    cout << "Enter a 8-bit sequence: ";
    // Store user-supplied sequence into the bitset
    cin >> eightBits;
    cout << endl;
    // create a copy
    bitset <8> flipInput (eightBits);
    return 0;
}

Initialize a bitset with hex number

#include <bitset>
#include <iostream>
using namespace std;
int main( ){
   const int num_lights = 15;
   const bitset<num_lights> outside( 0xf );
   const bitset<num_lights> inside( 0xff0 );
   const bitset<num_lights> driveway( 0x7000 );
}

instantiate a bitset object for 8 bits, given an unsigned long init value

#include <bitset>
#include <iostream>
#include <string>
int main ()
{
    using namespace std;
    bitset <8> eightbits (255);
    cout << "The initial contents of eightBits: " << eightbits << endl;
    return 0;
}

Instantiate a bitset object for holding 4 bits, all initialized to "0000"

#include <bitset>
#include <iostream>
#include <string>
int main ()
{
    using namespace std;
    bitset <4> fourBits;
    cout << fourBits << endl;
    return 0;
}

Instantiate a bitset object for holding 5 bits, initialize it to a bit sequence supplied by a string

#include <bitset>
#include <iostream>
#include <string>
int main ()
{
    using namespace std;
    bitset <5> fiveBits (string ("10101"));
    cout << fiveBits << endl;
    return 0;
}

Read a binary number into a bitset

#include <bitset>
#include <iostream>
#include <limits>
using namespace std;
int main( )
{
   // Read a binary number into a bitset
   cout << "Enter a binary number: ";
   bitset< numeric_limits<unsigned long>::digits > bits;
   cin >> bits;
   unsigned long decimal_equivalent = bits.to_ulong();
   cout  << "Binary number: " << bits << "\nDecimal equivalent: " << decimal_equivalent;
}

Reset bit in a bitset

#include <bitset>
#include <iostream>
using namespace std;
int main( ){
   const int num_lights = 15;
   const bitset<num_lights> outside( 0xf );
   const bitset<num_lights> inside( 0xff0 );
   const bitset<num_lights> driveway( 0x7000 );
   bitset<num_lights> lights;
   for( int i = 0; i < num_lights; i +=2 )
      lights.reset( i );
   cout << lights;
}

Test value in a bitset

#include <bitset>
#include <iostream>
using namespace std;
int main(int argc, char** argv){
  bitset<10> myBitset;
  myBitset.set(3);
  myBitset.set(6);
  myBitset[8] = true;
  myBitset[9] = myBitset[3];
  if (myBitset.test(3)) {
    cout << "Bit 3 is set!\n";
  }
  cout << myBitset << endl;
  return (0);
}

Use bitset with enum together

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <bitset>
#include <iostream>
using namespace std;
int main()
{
    /* enumeration type for the bits
     * - each bit represents a color
     */
    enum Color { red, yellow, green, blue, white, black, //...,
                 numColors };
    // create bitset for all bits/colors
    bitset<numColors> usedColors;
    // set bits for two colors
    usedColors.set(red);
    usedColors.set(blue);
    // print some bitset data
    cout << "bitfield of used colors:   " << usedColors
         << endl;
    cout << "number   of used colors:   " << usedColors.count()
         << endl;
    cout << "bitfield of unused colors: " << ~usedColors
         << endl;
    // if any color is used
    if (usedColors.any()) {
        // loop over all colors
        for (int c = 0; c < numColors; ++c) {
            // if the actual color is used
            if (usedColors[(Color)c]) {
                //...
            }
        }
    }
}
bitfield of used colors:   001001
number   of used colors:   2
bitfield of unused colors: 110110

write a decimal integer as a binary number

#include <bitset>
#include <iostream>
#include <limits>
using namespace std;
int main( )
{
   // write a decimal integer as a binary number
   int num = 100;
   cout  << "\n\nDecimal number: " << num << "\tBinary equivalent: " << bitset<8>(num) << endl;
}
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