proposition: Fact bt_insert_comm s t u : s→t→u = t→s→u.
proof: Proof. induction u as [ | u1 u2 IH ] using bt_rect'. + rew bt insert; bt insert case s t. + bt insert case t u1; bt insert case s u1; bt insert case s t; try bt lt cycle; f_equal; auto. Qed.
imports: List Arith Lia Max Wellfounded Setoid Eqdep_dec Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list utils_decidable finite seteq) Undecidability.Shared.Libs.DLW.Vec(pos) Undecidability.Shared.Libs.DLW.Wf(wf_finite wf_chains) Undecidability.FOL.TRAKHTENBROT(notations fol_ops)