Modular Arithmetic

Implement the function

val modulo : int -> int -> int

so that modulo n k is n mod k. Your implementation may not use the operator (mod), and must be tail recursive. The behavior of the function is undefined if n is negative or if k is not positive.

let _ = assert (modulo 10 3 = 1)
let _ = assert (modulo 7 7 = 0)
let _ = assert (modulo 0 5 = 0)