proposition: Lemma string_of_cont_comp : forall c d, string_of_cont (comp c d) = string_of_cont c ++ string_of_cont d.
proof: Proof. induction c; simpl; intros. refl. rewrite IHc. refl. Qed.
imports: CoLoR(LogicUtil RelUtil SN ListUtil Srs ATrs AUnary VecUtil EqUtil NatUtil ListMax)