bitset_bit_field.cpp

#include <bitset>
#include <iostream>
/*

1)A bitset is an array of bool but each Boolean value is not stored separately
instead bitset optimizes the space such that each bool takes 1 bit space only,
so space taken by bitset bs is less than that of bool bs[N] 2) N must be known
at compile time 3) The size of bitset is fixed at compile time that is, it can’t
be changed at runtime.
*/
// https://www.geeksforgeeks.org/c-bitset-interesting-facts/
// https://www.geeksforgeeks.org/c-bitset-and-its-application/

using namespace std;
int main() {
  const int M = sizeof(int) * 8;

  // default constructor initializes with all bits 0
  bitset<M> bset1;

  // bset2 is initialized with bits of 20
  bitset<M> bset2(20);

  // bset3 is initialized with bits of specified binary string
  bitset<M> bset3(string("1100"));

  // cout prints exact bits representation of bitset
  cout << bset1 << endl; // 00000000000000000000000000000000
  cout << bset2 << endl; // 00000000000000000000000000010100
  cout << bset3 << endl; // 00000000000000000000000000001100
  cout << endl;

  // declaring set8 with capacity of 8 bits

  bitset<8> set8; // 00000000

  // setting first bit (or 6th index)
  set8[1] = 1;       // 00000010
  set8[4] = set8[1]; // 00010010
  cout << set8 << endl;

  // count function returns number of set bits in bitset
  int numberof1 = set8.count();

  // size function returns total number of bits in bitset
  // so there difference will give us number of unset(0)
  // bits in bitset
  int numberof0 = set8.size() - numberof1;

  cout << set8 << " has " << numberof1 << " ones and " << numberof0
       << " zeros\n";

  // test function return 1 if bit is set else returns 0
  cout << "bool representation of " << set8 << " : ";
  for (std::size_t i = 0; i < set8.size(); i++)
    cout << set8.test(i) << " ";

  cout << endl;

  // any function returns true, if atleast 1 bit
  // is set
  if (!set8.any())
    cout << "set8 has no bit set.\n";

  if (!bset1.any())
    cout << "bset1 has no bit set.\n";

  // none function returns true, if none of the bit
  // is set
  if (!bset1.none())
    cout << "bset1 has some bit set\n";

  // bset.set() sets all bits
  cout << set8.set() << endl;

  // bset.set(pos, b) makes bset[pos] = b
  cout << set8.set(4, 0) << endl;

  // bset.set(pos) makes bset[pos] = 1  i.e. default
  // is 1
  cout << set8.set(4) << endl;

  // reset function makes all bits 0
  cout << set8.reset(2) << endl;
  cout << set8.reset() << endl;

  // flip function flips all bits i.e.  1 <-> 0
  // and  0 <-> 1
  cout << set8.flip(2) << endl;
  cout << set8.flip() << endl;

  // Converting decimal number to binary by using bitset
  int num = 100;
  bitset<8> set9(num);

  cout << "\nDecimal number: " << set9.to_ulong()
       << "  Binary equivalent: " << set9 << endl;
}