foo.to_ulong();

template <std::size_t N>
bool increase(std::bitset<N>& bs)
{
    for (std::size_t i = 0; i != bs.size(); ++i) {
        if (bs.flip(i).test(i) == true) {
            return true;
        }
    }
    return false; // overflow
}

std::bitset<20> bs;

do {
    std::cout << bs << std::endl;
} while (increase(bs));

bitset<20> b;

bool overflow = false;
while( ! overflow ){
    cout << b << endl; // prints bits in reversed order
    int ipos = b.size();
    overflow = true;
    while( overflow && --ipos >= 0 ){
        overflow = b[ipos];
        b[ipos] = ! b[ipos];
    }
}

#include<stdio.h>

      int  main()
      {
     int mask = 32768;
     unsigned int num = 15;
       while(mask > 0)
       {
      if((num & mask) ==0)
        printf("0");
       else
        printf("1");
    mask = mask >>1;

 }

}