It's a little verbose and can probably be reduced, but "((x % m) + m) % m" always works. Although it's probably not better than a check if x < 0 since branch pr

It's a little verbose and can probably be reduced, but "((x % m) + m) % m" always works. Although it's probably not better than a check if x < 0 since branch prediction will get that right almost always. I do think it's quite odd and frustrating that modulo can return negative numbers and I don't really get the reasoning there, but there's probably a good reason I don't know about.