Recursive exponentiation

Zayexponentiation.ml

let (<>) a b =
  let rec timesPrime a b acc = match b with
  | 0 -> acc
  | _ -> timesPrime a (pred b) (acc+a)
  in timesPrime a b 0
;;

let rec pow x = function
  | 0 -> 1
  | n when n mod 2 = 0 ->
      let x = pow  x (n/2) in
      (x <> x)
  | n -> (pow  x (n-1) <> x)
;;