proposition: Lemma valid_upath_rev: forall g p, valid_upath g p -> valid_upath g (rev p).
proof: Proof. induction p; intros. auto. simpl. apply valid_upath_concat. apply IHp. apply (valid_upath_tail' g p a H). rewrite <- rev_hd_last. destruct p. apply H. simpl. destruct H. apply adjacent_symm. apply H. Qed.
imports: Coq.Logic.Classical CertiGraph.lib.List_ext CertiGraph.lib.EquivDec_ext CertiGraph.graph.graph_model CertiGraph.graph.graph_relation CertiGraph.graph.path_lemmas CertiGraph.graph.graph_gen CertiGraph.graph.FiniteGraph