Count lines with ocaml standard library

lines_std.ml

let () =
  let n = ref 0 in
  let ic = open_in Sys.argv.(1) in
  (try
     while true; do
       ignore (input_line ic);
       incr n
     done;
     assert false
   with End_of_file -> ()
  );
  Printf.printf "%d\n" !n