proposition: Lemma svars_app l2 : forall l1, svars (l1 ++ l2) = svars l1 ++ svars l2.
proof: Proof. induction l1; simpl; intros. refl. rewrite IHl1, app_ass. refl. Qed.
imports: CoLoR(AInterpretation AContext VecUtil NatUtil LogicUtil ListUtil EqUtil)