proposition: Fact mb_is_pair_dec p x y : { p ≋ ⦃x,y⦄ } + { ~ p ≋ ⦃x,y⦄ }.
proof: Proof. Proof using Xfin Rdec. unfold mb_is_pair. apply (fol_quant_sem_dec fol_fa); auto; intros u. apply fol_equiv_dec; auto. apply (fol_bin_sem_dec fol_disj); auto. Qed.
imports: List Arith Nat Lia Max Wellfounded Coq.Setoids.Setoid Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list finite) Undecidability.Shared.Libs.DLW.Vec(pos vec) Undecidability.FOL.TRAKHTENBROT(notations fol_ops fo_sig fo_terms fo_logic)