In Scala, why could remainder (%) operator return a negative number?
For example, (-3) % 2 will return -1 instead of 1.
What is the preferred way to get the positive remainder in Scala? Such as (((-3) % 2) + 2) % 2, or abs(-3 % 2)?
Answer
In scala, why could remainder (%) operator return a negative number?
There are different conventions for the sign of the result of a modulo operation; Wikipedia has a good article on it. Scala, like most but by no means all programming languages, has the result take the sign of the dividend (the -3 in your case).
What is the preferred way to get the positive remainder in Scala?
I doubt there's a generally-agreed preferred way; if it were me, either use Math.floorMod, which gives a result with the sign of the divisor (2 in your example) instead of the dividend (this doesn't just mean the same value as % with a different sign, see the linked JavaDoc for details). Or just an if afterward (if (result < 0) { result += M; } [where M is the divisor, 2 in your example]).