proposition: Fact lb_meet_app l m a b : length l = length m -> (l++a)↓(m++b) = l↓m++a↓b.
proof: Proof. revert m; induction l as [ | x l IHl ]; intros [ | y m ]; try discriminate; intros H. + simpl; auto. + simpl app. rewrite lb_meet_cons; f_equal. apply IHl. simpl in H; inversion H; auto. Qed.
imports: List Lia Bool Setoid Undecidability.Shared.Libs.DLW.Utils(utils_tac)