proposition: Lemma ufroot_same_symm: forall u v, ufroot_same u v <-> ufroot_same v u.
proof: Proof. intros. unfold ufroot_same. split; intros; destruct H as [r [? ?]]; exists r; split; 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