proposition: Fact mb_equiv_dec x y : { x ≈ y } + { x ≉ y }.
proof: Proof. Proof using Xfin Rdec. destruct (mb_incl_dec x y); [ destruct (mb_incl_dec y x) | ]. 1: left; apply mb_equiv_eq; auto. all: right; rewrite mb_equiv_eq; tauto. 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)