open Printf

(** a simple symbol type *)
type option symbol_one = Ecks | Why | Zee "zed"

(** an example option type: options can be specified either short
 (-a, -b, -c, ...) or long with two dashes (--alpha, --bravo, --charlie, ...) *)
(*type option opts = {  *)
type option [short, long2] opts = {  
  (** these fields just use the default behavior: the types become
      option types, and provided arguments are assigned to the fields, which
      default to None if no argument is given. *)

  alpha:     int;
  bravo:     string;
  charlie:   float;
  delta:     bool; (* three possible values: Some true | Some false | None *)
  echo:      unit; (* note that unit option is effectively boolean *)
  foxtrot:   symbol_one; (* provided value must be ecks | why | zed *)

  (** these fields modify the default behavior in some simple ways *)

  golf:      default = 5; 
             help = "this is alpha"; 
             int;

  hotel:     key = "-x";       (* set key to -x (otherwise would be -h) *)
             string;

  india:     spec = "Clear";   (* -i sets india to false; otherwise it's true *)
             default = true; 
             bool;

  juliet:    spec = "Set";     (* -j sets juliet to Some true; otherwise None *)
             bool;

  kilo:      str = (Printf.sprintf "%.5f"); (* change print behavior *)
             float;

  (* some more complex behavior *)

  (* a silly example of how a more complex type can be used.  Note spec
     defaults to Arg.String since type isn't int, float, bool, unit, or symbol*)
  lima:      default = (0,0); 
             str = (fun (i0,i1) -> Printf.sprintf "%d,%d" i0 i1); 
             arg = (fun s -> lima := Scanf.sscanf s "%d,%d" (fun a b ->a,b));
             (int * int);


  (** every appearance of -v increases the verbosity level by one *)
  verbosity: spec = "Unit"; 
             arg = (fun () -> incr verbosity); 
             default = 0; 
             help = "increase verbosity level";
             int;

  (** this option has no corresponding field *)
  _:         arg = (fun () -> print_string "$Revision: 1.9 $\n"; exit 0);
             key = "-V";
             help = "print version and exit";
             unit;

}

let _ =
  let opts,args = parse_opts " [OPTS] arg0 arg1" in
  match args with 
  | [arg0; arg1] ->
    print_opts stdout opts;
    printf "args: [%s %s]\n" arg0 arg1
  | _ ->
    usage_opts ": Wrong number of arguments\nUsage: example [OPTS] arg0 arg1"