key.ml

let lwt_call f =
  let t1,w1 = Lwt.wait () in
  Lwt.ignore_result
    (let res = f () in
     Lwt.wakeup w1 res;
     Lwt.return_unit);
  t1
;;

let read_direction dir =
  lwt_call (fun () ->
            match Graphics.read_key () with
            ',' -> 0
           | 'e' -> 3
           | 'o' -> 6
           | 'a' -> 9
           | _   -> dir)
;;

let timeout_direction dir =
  lwt_call (fun () ->
            print_endline "before timeout";
            Lwt_unix.sleep delay ;
            print_endline "after timeout";
            dir )
;;
  
let get_direction dir =
  let t1 = read_direction dir
  and t2 = timeout_direction dir in
  Lwt.choose [t1;t2]
;;