Compute the parity of a number (two methods)

parity.cc

#include <iostream>

bool PairityA(int n) {
  bool res = 0;
  while(n) {
    res ^= n & 1;
    n >>= 1;
  }
  return res;
}

bool PairityB(int n) {
  int count = 0;
  while(n) {
    if (n&1) ++count;
    n >>= 1;
  }
  return (bool)(count % 2);
}

int main() {
  bool fail = false;
  for (int i = 0; i < 32; ++i) {
    if (PairityA(i) != PairityB(i)) {
      fail = true;
      std::cerr << "FAIL for " << i << std::endl;
      std::cerr << "A got " << PairityA(i) << ", B got " << PairityB(i) << std::endl;
    }
  }
  if (!fail) std::cerr << "Success!" << std::endl;
  return 0;
}