fact.ml

(* Open the big integer module, requires to compilate with "nums.cma" *)
open Big_int;;

(* Get the value as a big_int *)
let n = big_int_of_string Sys.argv.(1) in

(* Set up some big_int that we need use *)
let bi1 = big_int_of_int 1 in

(* The function *)
let rec fact_big_int n =
	if le_big_int n bi1 then bi1
	else mult_big_int n (fact_big_int (sub_big_int n bi1))
in

(* Compute and print *)
let result = string_of_big_int (fact_big_int n) in
Printf.printf "fact(%s) = %s\n" Sys.argv.(1) result;;