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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        *)
(************************************************************************)

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

(****************************************************************************)
(*                            Bruno Barras                                  *)
(****************************************************************************)

Require Import Relation_Definitions.
Require Import Relation_Operators.


Section Properties.

  Variable A : Set.
  Variable R : relation A.

  Let incl (R1 R2:relation A) : Prop := forall x y:A, R1 x y -> R2 x y.

Section Clos_Refl_Trans.

  Lemma clos_rt_is_preorder : preorder A (clos_refl_trans A R).
apply Build_preorder.
exact (rt_refl A R).

exact (rt_trans A R).
Qed.



Lemma clos_rt_idempotent :
 incl (clos_refl_trans A (clos_refl_trans A R)) (clos_refl_trans A R).
red in |- *.
induction 1; auto with sets.
intros.
apply rt_trans with y; auto with sets.
Qed.

  Lemma clos_refl_trans_ind_left :
   forall (A:Set) (R:A -> A -> Prop) (M:A) (P:A -> Prop),
     P M ->
     (forall P0 N:A, clos_refl_trans A R M P0 -> P P0 -> R P0 N -> P N) ->
     forall a:A, clos_refl_trans A R M a -> P a.
intros.
generalize H H0.
clear H H0.
elim H1; intros; auto with sets.
apply H2 with x; auto with sets.

apply H3.
apply H0; auto with sets.

intros.
apply H5 with P0; auto with sets.
apply rt_trans with y; auto with sets.
Qed.


End Clos_Refl_Trans.


Section Clos_Refl_Sym_Trans.

  Lemma clos_rt_clos_rst :
   inclusion A (clos_refl_trans A R) (clos_refl_sym_trans A R).
red in |- *.
induction 1; auto with sets.
apply rst_trans with y; auto with sets.
Qed.

  Lemma clos_rst_is_equiv : equivalence A (clos_refl_sym_trans A R).
apply Build_equivalence.
exact (rst_refl A R).

exact (rst_trans A R).

exact (rst_sym A R).
Qed.

  Lemma clos_rst_idempotent :
   incl (clos_refl_sym_trans A (clos_refl_sym_trans A R))
     (clos_refl_sym_trans A R).
red in |- *.
induction 1; auto with sets.
apply rst_trans with y; auto with sets.
Qed.

End Clos_Refl_Sym_Trans.

End Properties.