(* File gcd.ml *)
let rec gcd a b =
  if b = 0 then a
  else gcd b (a mod b);;

let main () =
  let len = Array.length Sys.argv in
  Printf.printf "array length %d\n" len;
  if len < 3 then begin
    Printf.printf "must have 2 args";
    exit 0;
  end;
  let a = int_of_string Sys.argv.(1) in
  let b = int_of_string Sys.argv.(2) in
  Printf.printf "gcd of %d and %d is %d\n" a b (gcd a b);
  exit 0;;
main ();;