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 subp_derives' {A}{agA: ageable A}:
forall P Q: pred A, (forall n, (P >=> Q) n) -> P |-- Q.