How to implement Bitcount using only Bitwise operators?

Question

The task is to implement a bit count logic using only bitwise operators. I got it working fine, but am wondering if someone can suggest a more elegant approach.

Onl

Answer 1

Several interesting solutions here.

If the solutions above are too boring, here is a C recursive version exempt of condition test or loop:

  int z(unsigned n, int count);
  int f(unsigned n, int count);

  int (*pf[2])(unsigned n, int count) = { z,f };

  int f(unsigned n, int count)
  {
     return (*pf[n > 0])(n >> 1, count+(n & 1));
  }

  int z(unsigned n, int count)
  {
     return count;
  }

  ...
  printf("%d\n", f(my_number, 0));