exception NegativeValue ;;

open Num ;;

let rec recursive = function
    Int 0 -> Int 1
  | n when n >/ Int 0 -> n */ recursive ( n -/ Int 1)
  | _ -> raise NegativeValue
;;

let rec tailRecursive = function
  | n when n </ Int 0 -> raise NegativeValue
  | n when n </ Int 2 -> Int 1
  | n ->
      let rec iterate i t =
        if ( i </ Int 2 ) then t
        else iterate ( i -/ Int 1) ( t */ i )
      in
      iterate n ( Int 1 )
;;