(* Contribution to the Coq Library   V6.3 (July 1999)                    *)
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(* File: axs_comprehension.v                                               *)
(* auteur: alex@sysal.ibp.fr                                               *)
(* date: 19/10/95                                                          *)
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Require Export axs_parties.
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(* Schema d'axiome de comprehension                                        *)
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Parameter subset : (E -> Prop) -> E -> E.
Axiom
axs_comprehension :
forall (F : E -> Prop) (a v0 : E), In v0 (subset F a) <-> In v0 a /\ F v0.
(* Proof of lem_comprehension_lr                                           *)
intros; elim (axs_comprehension F a v0); intros; exact (H0 H).
Qed.
(* End of proof of lem_comprehension_lr                                    *)
(* Proof of lem_comprehension_rl                                           *)
intros; elim (axs_comprehension F a v0); intros; exact (H1 H).
Qed.
(* End of proof of lem_comprehension_rl                                    *)
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(* Consequences                                                            *)
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(* Existence de l'ensemble vide                                            *)
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Definition def_F_vide (v0 : E) := v0 <> v0.
Definition vide (a : E) := subset def_F_vide a.
(* Proof of lem_vide_propertie                                             *)
intros; unfold vide in |- *; unfold def_F_vide in |- *; unfold not in |- *;
intros.
elim (axs_comprehension def_F_vide v1 v0); unfold def_F_vide in |- *;
unfold not in |- *; intros.
elim H0; clear H0; intros.
clear H; clear H1; clear H0; apply H2; clear H2; reflexivity.
apply H1; clear H1.
split.
elim (axs_comprehension def_F_vide v1 v0); unfold def_F_vide in |- *;
unfold not in |- *; intros.
elim H0; clear H0; intros; assumption.
elim (axs_comprehension def_F_vide v1 v0); unfold def_F_vide in |- *;
unfold not in |- *; intros.
elim H0; clear H0; intros.
apply H3; reflexivity.
assumption.
Qed.
(* End of proof of lem_vide_existence                                      *)
(* Proof of lem_vide_unicite                                               *)
intros; apply axs_extensionnalite; unfold iff in |- *; split; intros.
generalize (lem_vide_propertie v2 v0); intros; elim H0; assumption.
generalize (lem_vide_propertie v2 v1); intros; elim H0; assumption.
Qed.
(* End of proof of lem_vide_unicite                                        *)
Parameter var_vide : E.
Definition Vide := vide var_vide.

Lemma lem_x_inc_vide : forall x : E, inc x Vide -> x = Vide.