proposition: Lemma add_edge_evalid_rev: forall g e s t e', e<>e' -> evalid (pregraph_add_edge g e s t) e' -> evalid g e'.
proof: Proof. intros. simpl in H0. unfold addValidFunc in H0. destruct H0; [auto | symmetry in H0; contradiction]. Qed.
imports: Coq.Logic.ProofIrrelevance Coq.Sets.Ensembles Coq.Sets.Finite_sets Coq.Classes.Morphisms CertiGraph.lib.Coqlib CertiGraph.lib.Ensembles_ext CertiGraph.lib.relation_list CertiGraph.lib.List_ext CertiGraph.lib.Equivalence_ext CertiGraph.lib.EquivDec_ext VST.msl.Coqlib2 Coq.Lists.List CertiGraph.graph.graph_model CertiGraph.graph.path_lemmas CertiGraph.graph.reachable_ind