proposition: Fact hfs_cons_spec y x t : y ∈ hfs_cons x t <-> y = x \/ y ∈ t.
proof: Proof. unfold hfs_cons. rewrite btm_repr_cls; btm simpl. fol equiv. + rewrite <- bt_cls_hfs_repr_iff, bt_cls_hfs_repr; tauto. + tauto. Qed.
imports: List Arith Lia Max Wellfounded Setoid Eqdep_dec Bool Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list finite) Undecidability.Shared.Libs.DLW.Vec(pos vec) Undecidability.Shared.Libs.DLW.Wf(wf_finite wf_chains) Undecidability.FOL.TRAKHTENBROT(notations fol_ops membership btree)