type t1 = A | B
type t2 = Foo of string * t1

let print_t2 = function 
  Foo (s,t) -> let print_t1 = function A -> "A" | B -> "B" 
                in Printf.printf "Foo (\"%s\",%s)\n" s (print_t1 t)

open Camlp4.PreCast

let foo = Gram.Entry.mk "foo"
let bar = Gram.Entry.mk "bar"

EXTEND Gram
  GLOBAL: foo bar;
  foo: [ [ "foo"; i = LIDENT; b = bar -> Foo(i,b) ] ];
  bar: [ [ "?" -> A | "." -> B ] ];
END

let r = Gram.parse_string foo (Loc.mk "<string>") "foo x?"
  in print_t2 r

let _ = Gram.Entry.print Format.std_formatter foo

try
   DELETE_RULE Gram foo: "foo"; LIDENT; bar END
with Not_found -> Format.printf "@[no rule matched!@]@\n" 

(* the correct sentence 
let _ =
  try
    Gram.delete_rule foo
      [ Gram.Skeyword "foo";
        Gram.Stoken
          (((function | LIDENT ((_)) -> true | _ -> false), "LIDENT _"));
        Gram.Snterm (Gram.Entry.obj (bar : 'bar Gram.Entry.t)) ]
  with | Not_found -> Format.printf "@[no rule matched!@]@\n"
*)

let _ = Gram.Entry.print Format.std_formatter foo