Definition all_assertions_computable  :=
forall (Espec: OracleKind) psi tx vx (Q: assert),
exists k,  assert_safe Espec psi tx vx k = Q.
(* This is not generally true, but could be made true by adding an "assert" operator to the programming language *)

Lemma pred_sub_later' {A} `{H: ageable A}:
forall (P Q: pred A),
(|> P >=> |> Q)  |--  (|> (P >=> Q)).