proposition: Lemma same_set_contra: forall (U: Type) S1 S2 x, @Same_set U S1 S2 -> S1 x -> ~ S2 x -> False.
proof: Proof. intros. apply Ensembles.Extensionality_Ensembles in H. apply H1. rewrite <- H; trivial. Qed.
imports: CertiGraph.lib.Coqlib CertiGraph.lib.EquivDec_ext CertiGraph.lib.List_ext CertiGraph.lib.Ensembles_ext CertiGraph.lib.EnumEnsembles CertiGraph.graph.graph_model CertiGraph.graph.path_lemmas CertiGraph.graph.graph_gen CertiGraph.graph.MathGraph CertiGraph.graph.LstGraph CertiGraph.graph.FiniteGraph CertiGraph.graph.reachable_computable