rem

user=> (rem 10 9)
1
user=> (rem 2 2)
0

;; rem and mod are commonly used to get the remainder.
;; mod means Knuth's mod (truncating towards negativity). 
;; rem implements  ANSI C's % operator
;; Absolute value stays the same, always the distance
;; towards zero.
;; sign depends on dividend. 


user=> (rem -10 3)
-1
user=> (rem 10 -3)
1
user=> (rem -10 -3)
-1
user=> (rem  10 3)
1

user=> (mod -10 3)
2
user=> (mod 10 -3)
-2
user=> (mod -10 -3)
-1