testing keyboard input for a digit

Hi,

I am trying to test user's input to see if it contains a digit, but it is not going so well

let rec kbd () = 

  let ls = [0;1;2;3;4;5;6;7;8;9;] (* there doesn't seem to be a way of expressing a range 0..9 *)
  let rec find test = function
    | [] -> raise Not_found
    | hd :: tl -> if test hd then hd else find test tl in 

       print_string "Please enter an item number: ";
       try
          let item = read_line () in 

          if (item = find ls) then failwith "an item should contain a digit ";
          item
     with Failure msg -> (print_endline (msg ^ ", try again"); kbd ()) ;;

-: Error This expr "ls" has type int list but an expression was expected of type 'a -> bool

Thank you for any suggestion

jean