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(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016 *)
(* \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. *)
(****************************************************************************)
Require Export Ensembles.
Require Export Constructive_sets.
Require Export Relations_1.
Require Export Relations_1_facts.
Require Export Partial_Order.
Require Export Cpo.
Require Export Powerset.
Require Export Powerset_facts.
Require Export Classical.
Require Export Classical_sets.
Section Sets_as_an_algebra.
Variable U : Type.
Lemma sincl_add_x :
forall (A B:Ensemble U) (x:U),
~ In U A x ->
Strict_Included U (Add U A x) (Add U B x) -> Strict_Included U A B.
Proof.
intros A B x H' H'0; red.
lapply (Strict_Included_inv U (Add U A x) (Add U B x)); auto with sets.
clear H'0; intro H'0; split.
apply incl_add_x with (x := x); tauto.
elim H'0; intros H'1 H'2; elim H'2; clear H'0 H'2.
intros x0 H'0.
red; intro H'2.
elim H'0; clear H'0.
rewrite <- H'2; auto with sets.
Qed.
Lemma incl_soustr_in :
forall (X:Ensemble U) (x:U), In U X x -> Included U (Subtract U X x) X.
Proof.
intros X x H'; red.
intros x0 H'0; elim H'0; auto with sets.
Qed.
Lemma incl_soustr :
forall (X Y:Ensemble U) (x:U),
Included U X Y -> Included U (Subtract U X x) (Subtract U Y x).
Proof.
intros X Y x H'; red.
intros x0 H'0; elim H'0.
intros H'1 H'2.
apply Subtract_intro; auto with sets.
Qed.
Lemma incl_soustr_add_l :
forall (X:Ensemble U) (x:U), Included U (Subtract U (Add U X x) x) X.
Proof.
intros X x; red.
intros x0 H'; elim H'; auto with sets.
intro H'0; elim H'0; auto with sets.
intros t H'1 H'2; elim H'2; auto with sets.
Qed.
Lemma incl_soustr_add_r :
forall (X:Ensemble U) (x:U),
~ In U X x -> Included U X (Subtract U (Add U X x) x).
Proof.
intros X x H'; red.
intros x0 H'0; try assumption.
apply Subtract_intro; auto with sets.
red; intro H'1; apply H'; rewrite H'1; auto with sets.
Qed.
Hint Resolve incl_soustr_add_r: sets.
Lemma add_soustr_2 :
forall (X:Ensemble U) (x:U),
In U X x -> Included U X (Add U (Subtract U X x) x).
Proof.
intros X x H'; red.
intros x0 H'0; try assumption.
elim (classic (x = x0)); intro K; auto with sets.
elim K; auto with sets.
Qed.
Lemma add_soustr_1 :
forall (X:Ensemble U) (x:U),
In U X x -> Included U (Add U (Subtract U X x) x) X.
Proof.
intros X x H'; red.
intros x0 H'0; elim H'0; auto with sets.
intros y H'1; elim H'1; auto with sets.
intros t H'1; try assumption.
rewrite <- (Singleton_inv U x t); auto with sets.
Qed.
Lemma add_soustr_xy :
forall (X:Ensemble U) (x y:U),
x <> y -> Subtract U (Add U X x) y = Add U (Subtract U X y) x.
Proof.
intros X x y H'; apply Extensionality_Ensembles.
split; red.
intros x0 H'0; elim H'0; auto with sets.
intro H'1; elim H'1.
intros u H'2 H'3; try assumption.
apply Add_intro1.
apply Subtract_intro; auto with sets.
intros t H'2 H'3; try assumption.
elim (Singleton_inv U x t); auto with sets.
intros u H'2; try assumption.
elim (Add_inv U (Subtract U X y) x u); auto with sets.
intro H'0; elim H'0; auto with sets.
intro H'0; rewrite <- H'0; auto with sets.
Qed.
Lemma incl_st_add_soustr :
forall (X Y:Ensemble U) (x:U),
~ In U X x ->
Strict_Included U (Add U X x) Y -> Strict_Included U X (Subtract U Y x).
Proof.
intros X Y x H' H'0; apply sincl_add_x with (x := x); auto using add_soustr_1 with sets.
split.
elim H'0.
intros H'1 H'2.
generalize (Inclusion_is_transitive U).
intro H'4; red in H'4.
apply H'4 with (y := Y); auto using add_soustr_2 with sets.
red in H'0.
elim H'0; intros H'1 H'2; try exact H'1; clear H'0. (* PB *)
red; intro H'0; apply H'2.
rewrite H'0; auto 8 using add_soustr_xy, add_soustr_1, add_soustr_2 with sets.
Qed.
Lemma Sub_Add_new :
forall (X:Ensemble U) (x:U), ~ In U X x -> X = Subtract U (Add U X x) x.
Proof.
auto using incl_soustr_add_l with sets.
Qed.
Lemma Simplify_add :
forall (X X0:Ensemble U) (x:U),
~ In U X x -> ~ In U X0 x -> Add U X x = Add U X0 x -> X = X0.
Proof.
intros X X0 x H' H'0 H'1; try assumption.
rewrite (Sub_Add_new X x); auto with sets.
rewrite (Sub_Add_new X0 x); auto with sets.
rewrite H'1; auto with sets.
Qed.
Lemma Included_Add :
forall (X A:Ensemble U) (x:U),
Included U X (Add U A x) ->
Included U X A \/ (exists A' : _, X = Add U A' x /\ Included U A' A).
Proof.
intros X A x H'0; try assumption.
elim (classic (In U X x)).
intro H'1; right; try assumption.
exists (Subtract U X x).
split; auto using incl_soustr_in, add_soustr_xy, add_soustr_1, add_soustr_2 with sets.
red in H'0.
red.
intros x0 H'2; try assumption.
lapply (Subtract_inv U X x x0); auto with sets.
intro H'3; elim H'3; intros K K'; clear H'3.
lapply (H'0 x0); auto with sets.
intro H'3; try assumption.
lapply (Add_inv U A x x0); auto with sets.
intro H'4; elim H'4;
[ intro H'5; try exact H'5; clear H'4 | intro H'5; clear H'4 ].
elim K'; auto with sets.
intro H'1; left; try assumption.
red in H'0.
red.
intros x0 H'2; try assumption.
lapply (H'0 x0); auto with sets.
intro H'3; try assumption.
lapply (Add_inv U A x x0); auto with sets.
intro H'4; elim H'4;
[ intro H'5; try exact H'5; clear H'4 | intro H'5; clear H'4 ].
absurd (In U X x0); auto with sets.
rewrite <- H'5; auto with sets.
Qed.
Lemma setcover_inv :
forall A x y:Ensemble U,
covers (Ensemble U) (Power_set_PO U A) y x ->
Strict_Included U x y /\
(forall z:Ensemble U, Included U x z -> Included U z y -> x = z \/ z = y).
Proof.
intros A x y H'; elim H'.
unfold Strict_Rel_of; simpl.
intros H'0 H'1; split; [ auto with sets | idtac ].
intros z H'2 H'3; try assumption.
elim (classic (x = z)); auto with sets.
intro H'4; right; try assumption.
elim (classic (z = y)); auto with sets.
intro H'5; try assumption.
elim H'1.
exists z; auto with sets.
Qed.
Theorem Add_covers :
forall A a:Ensemble U,
Included U a A ->
forall x:U,
In U A x ->
~ In U a x -> covers (Ensemble U) (Power_set_PO U A) (Add U a x) a.
Proof.
intros A a H' x H'0 H'1; try assumption.
apply setcover_intro; auto with sets.
red.
split; [ idtac | red; intro H'2; try exact H'2 ]; auto with sets.
apply H'1.
rewrite H'2; auto with sets.
red; intro H'2; elim H'2; clear H'2.
intros z H'2; elim H'2; intros H'3 H'4; try exact H'3; clear H'2.
lapply (Strict_Included_inv U a z); auto with sets; clear H'3.
intro H'2; elim H'2; intros H'3 H'5; elim H'5; clear H'2 H'5.
intros x0 H'2; elim H'2.
intros H'5 H'6; try assumption.
generalize H'4; intro K.
red in H'4.
elim H'4; intros H'8 H'9; red in H'8; clear H'4.
lapply (H'8 x0); auto with sets.
intro H'7; try assumption.
elim (Add_inv U a x x0); auto with sets.
intro H'15.
cut (Included U (Add U a x) z).
intro H'10; try assumption.
red in K.
elim K; intros H'11 H'12; apply H'12; clear K; auto with sets.
rewrite H'15.
red.
intros x1 H'10; elim H'10; auto with sets.
intros x2 H'11; elim H'11; auto with sets.
Qed.
Theorem covers_Add :
forall A a a':Ensemble U,
Included U a A ->
Included U a' A ->
covers (Ensemble U) (Power_set_PO U A) a' a ->
exists x : _, a' = Add U a x /\ In U A x /\ ~ In U a x.
Proof.
intros A a a' H' H'0 H'1; try assumption.
elim (setcover_inv A a a'); auto with sets.
intros H'6 H'7.
clear H'1.
elim (Strict_Included_inv U a a'); auto with sets.
intros H'5 H'8; elim H'8.
intros x H'1; elim H'1.
intros H'2 H'3; try assumption.
exists x.
split; [ try assumption | idtac ].
clear H'8 H'1.
elim (H'7 (Add U a x)); auto with sets.
intro H'1.
absurd (a = Add U a x); auto with sets.
red; intro H'8; try exact H'8.
apply H'3.
rewrite H'8; auto with sets.
auto with sets.
red.
intros x0 H'1; elim H'1; auto with sets.
intros x1 H'8; elim H'8; auto with sets.
split; [ idtac | try assumption ].
red in H'0; auto with sets.
Qed.
Theorem covers_is_Add :
forall A a a':Ensemble U,
Included U a A ->
Included U a' A ->
(covers (Ensemble U) (Power_set_PO U A) a' a <->
(exists x : _, a' = Add U a x /\ In U A x /\ ~ In U a x)).
Proof.
intros A a a' H' H'0; split; intro K.
apply covers_Add with (A := A); auto with sets.
elim K.
intros x H'1; elim H'1; intros H'2 H'3; rewrite H'2; clear H'1.
apply Add_covers; intuition.
Qed.
Theorem Singleton_atomic :
forall (x:U) (A:Ensemble U),
In U A x ->
covers (Ensemble U) (Power_set_PO U A) (Singleton U x) (Empty_set U).
Proof.
intros x A H'.
rewrite <- (Empty_set_zero' U x).
apply Add_covers; auto with sets.
Qed.
Lemma less_than_singleton :
forall (X:Ensemble U) (x:U),
Strict_Included U X (Singleton U x) -> X = Empty_set U.
Proof.
intros X x H'; try assumption.
red in H'.
lapply (Singleton_atomic x (Full_set U));
[ intro H'2; try exact H'2 | apply Full_intro ].
elim H'; intros H'0 H'1; try exact H'1; clear H'.
elim (setcover_inv (Full_set U) (Empty_set U) (Singleton U x));
[ intros H'6 H'7; try exact H'7 | idtac ]; auto with sets.
elim (H'7 X); [ intro H'5; try exact H'5 | intro H'5 | idtac | idtac ];
auto with sets.
elim H'1; auto with sets.
Qed.
End Sets_as_an_algebra.
Hint Resolve incl_soustr_in: sets.
Hint Resolve incl_soustr: sets.
Hint Resolve incl_soustr_add_l: sets.
Hint Resolve incl_soustr_add_r: sets.
Hint Resolve add_soustr_1 add_soustr_2: sets.
Hint Resolve add_soustr_xy: sets.
|
