(***********************************************************************)
(*                                                                     *)
(*                               TAToo                                 *)
(*                                                                     *)
(*                     Kim Nguyen, LRI UMR8623                         *)
(*                   Université Paris-Sud & CNRS                       *)
(*                                                                     *)
(*  Copyright 2010-2012 Université Paris-Sud and Centre National de la *)
(*  Recherche Scientifique. All rights reserved.  This file is         *)
(*  distributed under the terms of the GNU Lesser General Public       *)
(*  License, with the special exception on linking described in file   *)
(*  ../LICENSE.                                                        *)
(*                                                                     *)
(***********************************************************************)

(*
  Time-stamp: <Last modified on 2013-03-09 11:16:45 CET by Kim Nguyen>
*)

module type ATOM =
sig
  type t
  val neg : t -> t
  include Utils.Hcons.Abstract with type t := t
  include Utils.Common_sig.Printable with type t := t
end

type ('formula,'atom) expr =
  | False
  | True
  | Or of 'formula * 'formula
  | And of 'formula * 'formula
  | Atom of 'atom

(** View of the internal representation of a formula,
    used for pattern matching *)

module Make(P : ATOM) :
sig
  type t

  (** Abstract type representing hashconsed formulae *)

  val hash : t -> int
  (** Hash function for formulae *)

  val uid : t -> Utils.Uid.t
  (** Returns a unique ID for formulae *)

  val equal : t -> t -> bool
  (** Equality over formulae *)

  val expr : t -> (t,P.t) expr
  (** Return a view of the formulae *)

  val compare : t -> t -> int
  (** Comparison of formulae *)

  val print : Format.formatter -> t -> unit
  (** Pretty printer *)

  val is_true : t -> bool
  (** [is_true f] tests whether the formula is the atom True *)

  val is_false : t -> bool
  (** [is_false f] tests whether the formula is the atom False *)

  val true_ : t
  (** Atom True *)

  val false_ : t
  (** Atom False *)

  val atom_ : P.t -> t
  (** [atom_ dir b q] creates a down_left or down_right atom for state
      [q]. The atom is positive if [b == true].
  *)

  val not_ : t -> t
  val or_ : t -> t -> t
  val and_ : t -> t -> t
  (** Boolean connective *)

  val of_bool : bool -> t
  (** Convert an ocaml Boolean value to a formula *)

  val fold : (t -> 'a -> 'a) -> t -> 'a -> 'a
  (** [fold f phi acc] folds [f] over the formula structure *)

end