proposition: Fact mb_is_opair_fun p q x y : p ≋ ⦅x,y⦆ -> q ≋ ⦅x,y⦆ -> p ≈ q.
proof: Proof. Proof using mb_axiom_ext. intros (a & b & H1 & H2 & H3) (u & v & G1 & G2 & G3). generalize (mb_is_pair_fun H1 G1) (mb_is_pair_fun H2 G2); intros E1 E2. rewrite E1, E2 in H3. revert H3 G3; apply mb_is_pair_fun. 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)