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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: Powerset.v,v 1.5.2.1 2004/07/16 19:31:18 herbelin Exp $ i*)
+
+Require Export Ensembles.
+Require Export Relations_1.
+Require Export Relations_1_facts.
+Require Export Partial_Order.
+Require Export Cpo.
+
+Section The_power_set_partial_order.
+Variable U : Type.
+
+Inductive Power_set (A:Ensemble U) : Ensemble (Ensemble U) :=
+ Definition_of_Power_set :
+ forall X:Ensemble U, Included U X A -> In (Ensemble U) (Power_set A) X.
+Hint Resolve Definition_of_Power_set.
+
+Theorem Empty_set_minimal : forall X:Ensemble U, Included U (Empty_set U) X.
+intro X; red in |- *.
+intros x H'; elim H'.
+Qed.
+Hint Resolve Empty_set_minimal.
+
+Theorem Power_set_Inhabited :
+ forall X:Ensemble U, Inhabited (Ensemble U) (Power_set X).
+intro X.
+apply Inhabited_intro with (Empty_set U); auto with sets.
+Qed.
+Hint Resolve Power_set_Inhabited.
+
+Theorem Inclusion_is_an_order : Order (Ensemble U) (Included U).
+auto 6 with sets.
+Qed.
+Hint Resolve Inclusion_is_an_order.
+
+Theorem Inclusion_is_transitive : Transitive (Ensemble U) (Included U).
+elim Inclusion_is_an_order; auto with sets.
+Qed.
+Hint Resolve Inclusion_is_transitive.
+
+Definition Power_set_PO : Ensemble U -> PO (Ensemble U).
+intro A; try assumption.
+apply Definition_of_PO with (Power_set A) (Included U); auto with sets.
+Defined.
+Hint Unfold Power_set_PO.
+
+Theorem Strict_Rel_is_Strict_Included :
+ same_relation (Ensemble U) (Strict_Included U)
+ (Strict_Rel_of (Ensemble U) (Power_set_PO (Full_set U))).
+auto with sets.
+Qed.
+Hint Resolve Strict_Rel_Transitive Strict_Rel_is_Strict_Included.
+
+Lemma Strict_inclusion_is_transitive_with_inclusion :
+ forall x y z:Ensemble U,
+ Strict_Included U x y -> Included U y z -> Strict_Included U x z.
+intros x y z H' H'0; try assumption.
+elim Strict_Rel_is_Strict_Included.
+unfold contains in |- *.
+intros H'1 H'2; try assumption.
+apply H'1.
+apply Strict_Rel_Transitive_with_Rel with (y := y); auto with sets.
+Qed.
+
+Lemma Strict_inclusion_is_transitive_with_inclusion_left :
+ forall x y z:Ensemble U,
+ Included U x y -> Strict_Included U y z -> Strict_Included U x z.
+intros x y z H' H'0; try assumption.
+elim Strict_Rel_is_Strict_Included.
+unfold contains in |- *.
+intros H'1 H'2; try assumption.
+apply H'1.
+apply Strict_Rel_Transitive_with_Rel_left with (y := y); auto with sets.
+Qed.
+
+Lemma Strict_inclusion_is_transitive :
+ Transitive (Ensemble U) (Strict_Included U).
+apply cong_transitive_same_relation with
+ (R := Strict_Rel_of (Ensemble U) (Power_set_PO (Full_set U)));
+ auto with sets.
+Qed.
+
+Theorem Empty_set_is_Bottom :
+ forall A:Ensemble U, Bottom (Ensemble U) (Power_set_PO A) (Empty_set U).
+intro A; apply Bottom_definition; simpl in |- *; auto with sets.
+Qed.
+Hint Resolve Empty_set_is_Bottom.
+
+Theorem Union_minimal :
+ forall a b X:Ensemble U,
+ Included U a X -> Included U b X -> Included U (Union U a b) X.
+intros a b X H' H'0; red in |- *.
+intros x H'1; elim H'1; auto with sets.
+Qed.
+Hint Resolve Union_minimal.
+
+Theorem Intersection_maximal :
+ forall a b X:Ensemble U,
+ Included U X a -> Included U X b -> Included U X (Intersection U a b).
+auto with sets.
+Qed.
+
+Theorem Union_increases_l : forall a b:Ensemble U, Included U a (Union U a b).
+auto with sets.
+Qed.
+
+Theorem Union_increases_r : forall a b:Ensemble U, Included U b (Union U a b).
+auto with sets.
+Qed.
+
+Theorem Intersection_decreases_l :
+ forall a b:Ensemble U, Included U (Intersection U a b) a.
+intros a b; red in |- *.
+intros x H'; elim H'; auto with sets.
+Qed.
+
+Theorem Intersection_decreases_r :
+ forall a b:Ensemble U, Included U (Intersection U a b) b.
+intros a b; red in |- *.
+intros x H'; elim H'; auto with sets.
+Qed.
+Hint Resolve Union_increases_l Union_increases_r Intersection_decreases_l
+ Intersection_decreases_r.
+
+Theorem Union_is_Lub :
+ forall A a b:Ensemble U,
+ Included U a A ->
+ Included U b A ->
+ Lub (Ensemble U) (Power_set_PO A) (Couple (Ensemble U) a b) (Union U a b).
+intros A a b H' H'0.
+apply Lub_definition; simpl in |- *.
+apply Upper_Bound_definition; simpl in |- *; auto with sets.
+intros y H'1; elim H'1; auto with sets.
+intros y H'1; elim H'1; simpl in |- *; auto with sets.
+Qed.
+
+Theorem Intersection_is_Glb :
+ forall A a b:Ensemble U,
+ Included U a A ->
+ Included U b A ->
+ Glb (Ensemble U) (Power_set_PO A) (Couple (Ensemble U) a b)
+ (Intersection U a b).
+intros A a b H' H'0.
+apply Glb_definition; simpl in |- *.
+apply Lower_Bound_definition; simpl in |- *; auto with sets.
+apply Definition_of_Power_set.
+generalize Inclusion_is_transitive; intro IT; red in IT; apply IT with a;
+ auto with sets.
+intros y H'1; elim H'1; auto with sets.
+intros y H'1; elim H'1; simpl in |- *; auto with sets.
+Qed.
+
+End The_power_set_partial_order.
+
+Hint Resolve Empty_set_minimal: sets v62.
+Hint Resolve Power_set_Inhabited: sets v62.
+Hint Resolve Inclusion_is_an_order: sets v62.
+Hint Resolve Inclusion_is_transitive: sets v62.
+Hint Resolve Union_minimal: sets v62.
+Hint Resolve Union_increases_l: sets v62.
+Hint Resolve Union_increases_r: sets v62.
+Hint Resolve Intersection_decreases_l: sets v62.
+Hint Resolve Intersection_decreases_r: sets v62.
+Hint Resolve Empty_set_is_Bottom: sets v62.
+Hint Resolve Strict_inclusion_is_transitive: sets v62. \ No newline at end of file