proposition: Lemma pfoot_cons: forall (g: PreGraph V E) l e v, valid_path g (v, e::l) -> pfoot g (v,(e::l)) = pfoot g (dst g e, l).
proof: Proof. intros. destruct l; simpl. reflexivity. apply (pfoot_head_irrel l g v (dst g e) e0). 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