sexp formatter

format_sexp.ml

(*
 * ocamlfind ocamlopt -linkpkg -syntax camlp4o
 *   -package lwt,lwt.syntax,lwt.unix,sexplib
 *   format_sexp.ml -o format_sexp
 *)
 
open Lwt
open Sexplib

let catch f =
  try Some (f ()) with _ -> None

let main fileo =
  lwt input =
    match fileo with
    | None      -> return Lwt_io.stdin
    | Some file -> Lwt_io.(open_file ~mode:Input file)
  in
  lwt sexp =
    let stream = Lwt_io.read_lines input in
    Lwt_stream.fold (^) stream "" >|= Sexp.of_string in
  Lwt_io.printl Sexp.(to_string_hum sexp)

let _ =
  Lwt_main.run @@ main (catch @@ fun () -> Sys.argv.(1))