proposition: Lemma red_rev : forall R t u, red R t u -> red (reverses R) (rev' t) (rev' u).
proof: Proof. intros. redtac. unfold fill. rewrite !rev'_app, !app_ass. ex (rev' l) (rev' r) (mkContext (rev' (rgt c)) (rev' (lft c))). intuition. change (In (reverse (mkRule l r)) (reverses R)). apply in_map. exact H. Qed.
imports: CoLoR(Srs ListUtil RelUtil LogicUtil SN)