It's a bit different: Scheme: > (mod 5 2) 1 > (mod 5 -2) 1 > (mod -5 2) 1 > (mod -5 -2) 1 > (remainder 5 2) 1 > (remainder 5 -2) 1 >

It's a bit different: Scheme: > (mod 5 2) 1 > (mod 5 -2) 1 > (mod -5 2) 1 > (mod -5 -2) 1 > (remainder 5 2) 1 > (remainder 5 -2) 1 > (remainder -5 2) -1 > (remainder -5 -2) -1 Haskell: Prelude> a = 5 :: Integer Prelude> b = 2 :: Integer Prelude> mod a b 1 Prelude> mod a (-b) -1 Prelude> mod (-a) b 1 Prelude> mod (-a) (-b) -1 Prelude> rem a b 1 Prelude> rem a (-b) 1 Prelude> rem (-a) b -1 Prelude> rem (-a) (-b) -1 So in Scheme mod is the Euclidean modulus (always >= 0) and remainder takes the sign of the dividend (comes from truncated division, same as C's %). In Haskell mod takes the sign of the divisor (floored division, same as Python), while rem behaves the same way as Scheme's remainder or C's %. I prefer Scheme's way, because it was what we always used in classes when I studied maths. mod returning a negative number is just too weird. EDIT: It appears that Scheme also has modulo, which comes from floored division: > (modulo 5 2) 1 > (modulo 5 -2) -1 > (modulo -5 2) 1 > (modulo -5 -2) -1