proposition: Fact gfp_equiv : equiv _ gfp.
proof: Proof. Proof using i_trans i_sym i_refl gfp_trans gfp_sym gfp_refl HF3 HF2 HF1. msplit 2. + intro; apply gfp_refl; auto. + intros ? y ? ? ?; apply gfp_trans; exists y; auto. + intros ? ?; apply gfp_sym. Qed.
imports: List Arith Nat Lia Relations Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list finite php) Undecidability.FOL.TRAKHTENBROT(notations)