(* Lemma subp_later {A} `{agA:  ageable A} (SS: natty A): forall (P Q: pred A), |> (P >=> Q) |-- |> P >=> |> Q. *)

Lemma subp_unfash {A} `{Age_alg A}:
forall (P Q : pred nat) (n: nat), (P >=> Q) n -> ( ! P >=> ! Q) n.