code: func LogDist(a, b ID) int {
  	lz := 0
  	for i := range a {
  		x := a[i] ^ b[i]
  		if x == 0 {
  			lz += 8
  		} else {
  			lz += bits.LeadingZeros8(x)
  			break
  		}
  	}
  	return len(a)*8 - lz
  }
docs: // LogDist returns the logarithmic distance between a and b, log2(a ^ b).