22 replies to this topic

[patrrr]

#define COPY_BIT(x, i, y, j) (y) = ((y) & ~(1 << (j))) | ((((x) >> (i)) & 1) << (j))

Something like that...? Can probably be optimized better.

Edited by patrrr, 17 October 2012 - 06:33 AM.

[Álvaro]

What patrrr wrote seems correct. I would do it with a function, though:

unsigned copy_bit(unsigned x, int i, unsigned y, int j) {
  y &= ~(1u << j); // Clear y's j-th bit
  y |= ((x >> i) & 1u) << j; // Copy x's i-th bit into position j
  return y;
}

The fact that you need to use some funky name for the type and that you are going for lots of generality is only confusing matters, so start without that.

[Misery]

@alvaro & @patrrr: Thanks a lot Guys. That was exactly the thing I was looking for.
alvaro: at the moment I cannot even count how many times you have halped me. Special thanks and huge respect to your skills!