proposition: Lemma star_cons: forall (L:language) w1 w2 w3, In w1 L -> In w2 (Star L) -> w3 = w1 ++ w2 -> In w3 (Star L).
proof: Proof. intros. destruct H0 as (n, Hp). exists (S n). subst. apply pow_cons_eq; auto. Qed.
imports: Coq.Lists.List