exception No_output

let () =
  let usage = "" in
  let backend = ref "c" in
  let file = ref None in
  let ismodule = ref false in
  let arguments = [
    "--backend", Arg.Set_string backend, "set backend (default \"c\")";
    "--module" , Arg.Set ismodule , "build the source as a module";
  ]
  in
    Arg.parse arguments (fun x -> file := Some x) usage;
    let channel =
      match !file with
        | None -> stdin
        | Some f -> open_in f
    in
    let buf = Lexing.from_channel channel in
    let ast =
      try
        Parser.main Lexer.token buf
      with
        | Lexer.Error msg ->
	        Printf.fprintf stderr "%s%!" msg;
            exit 1
        | Parser.Error ->
	        Printf.fprintf stderr "At offset %d: syntax error.\n%!" (Lexing.lexeme_start buf);
            exit 1
    in
      (match !backend with
         | "echo" -> Echo.print ast
         | "c"    -> C.print !ismodule !file ast
         | _ -> failwith "Unknown backend"
      );
      close_in channel;
      ()