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(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)
(****************************************************************************)
(*                                                                          *)
(*                         Naive Set Theory in Coq                          *)
(*                                                                          *)
(*                     INRIA                        INRIA                   *)
(*              Rocquencourt                        Sophia-Antipolis        *)
(*                                                                          *)
(*                                 Coq V6.1                                 *)
(*									    *)
(*			         Gilles Kahn 				    *)
(*				 Gerard Huet				    *)
(*									    *)
(*									    *)
(*                                                                          *)
(* Acknowledgments: This work was started in July 1993 by F. Prost. Thanks  *)
(* to the Newton Institute for providing an exceptional work environment    *)
(* in Summer 1995. Several developments by E. Ledinot were an inspiration.  *)
(****************************************************************************)

(*i $Id: Cpo.v 8642 2006-03-17 10:09:02Z notin $ i*)

Require Export Ensembles.
Require Export Relations_1.
Require Export Partial_Order.

Section Bounds.
Variable U : Type.
Variable D : PO U.

Let C := Carrier_of U D.

Let R := Rel_of U D.

Inductive Upper_Bound (B:Ensemble U) (x:U) : Prop :=
    Upper_Bound_definition :
      In U C x -> (forall y:U, In U B y -> R y x) -> Upper_Bound B x.

Inductive Lower_Bound (B:Ensemble U) (x:U) : Prop :=
    Lower_Bound_definition :
      In U C x -> (forall y:U, In U B y -> R x y) -> Lower_Bound B x.

Inductive Lub (B:Ensemble U) (x:U) : Prop :=
    Lub_definition :
      Upper_Bound B x -> (forall y:U, Upper_Bound B y -> R x y) -> Lub B x.

Inductive Glb (B:Ensemble U) (x:U) : Prop :=
    Glb_definition :
      Lower_Bound B x -> (forall y:U, Lower_Bound B y -> R y x) -> Glb B x.

Inductive Bottom (bot:U) : Prop :=
    Bottom_definition :
      In U C bot -> (forall y:U, In U C y -> R bot y) -> Bottom bot.

Inductive Totally_ordered (B:Ensemble U) : Prop :=
    Totally_ordered_definition :
      (Included U B C ->
       forall x y:U, Included U (Couple U x y) B -> R x y \/ R y x) ->
      Totally_ordered B.

Definition Compatible : Relation U :=
  fun x y:U =>
    In U C x ->
    In U C y ->  exists z : _, In U C z /\ Upper_Bound (Couple U x y) z.
	
Inductive Directed (X:Ensemble U) : Prop :=
    Definition_of_Directed :
      Included U X C ->
      Inhabited U X ->
      (forall x1 x2:U,
         Included U (Couple U x1 x2) X ->
          exists x3 : _, In U X x3 /\ Upper_Bound (Couple U x1 x2) x3) ->
      Directed X.

Inductive Complete : Prop :=
    Definition_of_Complete :
      (exists bot : _, Bottom bot) ->
      (forall X:Ensemble U, Directed X ->  exists bsup : _, Lub X bsup) ->
      Complete.

Inductive Conditionally_complete : Prop :=
    Definition_of_Conditionally_complete :
      (forall X:Ensemble U,
         Included U X C ->
         (exists maj : _, Upper_Bound X maj) ->
          exists bsup : _, Lub X bsup) -> Conditionally_complete.
End Bounds.
Hint Resolve Totally_ordered_definition Upper_Bound_definition
  Lower_Bound_definition Lub_definition Glb_definition Bottom_definition
  Definition_of_Complete Definition_of_Complete
  Definition_of_Conditionally_complete.

Section Specific_orders.
Variable U : Type.

Record Cpo : Type := Definition_of_cpo
  {PO_of_cpo : PO U; Cpo_cond : Complete U PO_of_cpo}.

Record Chain : Type := Definition_of_chain
  {PO_of_chain : PO U;
   Chain_cond : Totally_ordered U PO_of_chain (Carrier_of U PO_of_chain)}.

End Specific_orders.