proposition: Corollary valid_path_cons: forall (g: PreGraph V E) v a l, valid_path g (v,a::l) -> valid_path g (dst g a, l).
proof: Proof. unfold valid_path; intros. destruct H. destruct l. apply H0. split. apply H0. apply (valid_path'_cons g (e::l) a H0). 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