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(*                                                                        *)
(*  Menhir                                                                *)
(*                                                                        *)
(*  François Pottier and Yann Régis-Gianas, INRIA Rocquencourt            *)
(*                                                                        *)
(*  Copyright 2005 Institut National de Recherche en Informatique et      *)
(*  en Automatique. All rights reserved. This file is distributed         *)
(*  under the terms of the Q Public License version 1.0, with the         *)
(*  change described in file LICENSE.                                     *)
(*                                                                        *)
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(** This module implements a very simple notion of ``mark''. *)

(** The type of marks. *)
type t

(** [fresh()] generates a fresh mark, that is, a mark that is guaranteed
    to be distinct from all existing marks. *)
val fresh: unit -> t

(** [same mark1 mark2] tells whether [mark1] and [mark2] are the same
    mark, that is, were created by the same call to [fresh]. *)
val same: t -> t -> bool

(** [none] is a distinguished mark, created via an initial call to
    [fresh()]. *)
val none: t