Yes, this is what we want, because if `$total == 0` and `$total = $used + $free` then `$used = 0`.  Thus `$relative` is always `0` when `$total` is `0`, but `$total` was previously bumped to `1` so that you wouldn't get the division by zero error.

I think the new code is more clear than the old, and certainly more clear than transitioning to complex numbers.