(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2010     *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

open Xml_datatype

type t

val equal : t -> t -> bool
val compare : t -> t -> int

val initial : t
val dummy : t
val fresh : unit -> t
val to_string : t -> string
val of_int : int -> t
val to_int : t -> int
val newer_than : t -> t -> bool

(* XML marshalling *)
val to_xml : t -> xml
val of_xml : xml -> t

(* Attaches to an exception the concerned state id, plus an optional
 * state id that is a valid state id before the error.
 * Backtracking to the valid id is safe.
 * The initial_state_id is assumed to be safe. *)
val add : exn -> ?valid:t -> t -> exn
val get : exn -> (t * t) option