How do you do modulo or remainder in Erlang?

Question

I\'m brand new to Erlang. How do you do modulo (get the remainder of a division)? It\'s % in most C-like languages, but that designates a comment in Erlang.

Several

Answer 1

The accepted answer is wrong.

rem behaves exactly like the % operator in modern C. It uses truncated division.

The accepted answer fails for X<0 and Y<0. Consider mod(-5,-3):

C:                     -5 % -3 == -2
rem:                 -5 rem -3 == -2
Y + X rem Y:    -3 + -5 rem -3 == -5 !! wrong !!

The alternative implementations for the modulo operator use floored division and Euclidean division. The results for those are

flooring division:   -5 mod -3 == -2
euclidean division:  -5 mod -3 == 1

So

Y + X rem Y

doesn't reproduce any modulo operator for X < 0 and Y < 0.

And rem works as expected -- it's using truncated division.

Answer 2

Erlang remainder not works with negative numbers, so you have to write your own function for negative parameters.