C++ Bitsets

Constructors

  bitset();
  bitset( unsigned long val );

Bitsets can either be constructed with no arguments or with an unsigned long number val that will be converted into binary and inserted into the bitset. When creating bitsets, the number given in the place of the template determines how long the bitset is.

For example, the following code creates two bitsets and displays them:

  // create a bitset that is 8 bits long
  bitset<8> bs;

  // display that bitset
  for( int i = (int) bs.size(); i >= 0; i-- ) {
    cout << bs[i] << " ";
  }
  cout << endl;

  // create a bitset out of a number
  bitset<8> bs2( (long) 131 );

  // display that bitset, too
  for( int i = (int) bs2.size(); i >= 0; i-- ) {
    cout << bs2[i] << " ";
  }
  cout << endl;

Operators

  !=, ==, &=, ^=, |=, ~, <<=, >>=, []

These operators all work with bitsets. They can be described as follows:

• != returns true if the two bitsets are not equal.
• == returns true if the two bitsets are equal.
• &= performs the AND operation on the two bitsets.
• ^= performs the XOR operation on the two bitsets.
• |= performs the OR operation on the two bitsets.
• ~ reverses the bitset (same as calling flip())
• <<= shifts the bitset to the left
• >>= shifts the bitset to the right
• [x] returns a reference to the xth bit in the bitset.

For example, the following code creates a bitset and shifts it to the left 4 places:

  // create a bitset out of a number
  bitset<8> bs2( (long) 131 );

  cout << "bs2 is " << bs2 << endl;

  // shift the bitset to the left by 4 digits
  bs2 <<= 4;

  cout << "now bs2 is " << bs2 << endl;

When the above code is run, it displays:

  bs2 is 10000011
  now bs2 is 00110000

any

  bool any();

The any() function returns true if any bit of the bitset is 1, otherwise, it returns false.

count

  size_type count();

The function count() returns the number of bits that are set to 1 in the bitset.

flip

  bitset &flip();
  bitset &flip( size_t pos );

The flip() function inverts all of the bits in the bitset, and returns the bitset. If pos is specified, only the bit at position pos is flipped.

none

  bool none();

The none() function only returns true if none of the bits in the bitset are set to 1.

reset

  bitset &reset();
  bitset &reset( size_t pos );

The reset() fucntion clears all of the bits in the bitset, and returns the bitset. If pos is specified, then only the bit at position pos is cleared.

set

  bitset &set();
  bitset &set( size_t pos, int val=1 );

The set() fucntion sets all of the bits in the bitset, and returns the bitset. If pos is specified, then only the bit at position pos is set.

size

  size_t size();

The size() function returns the number of bits that the bitset can hold.

test

  bool test( size_t pos );

The function test() returns the value of the bit at position pos.

to_string

  string to_string();

The to_string() function returns a string representation of the bitset.

to_ulong

  unsigned long to_ulong();

The function to_ulong() returns the bitset, converted into an unsigned long integer.