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 proj_frame_ret_assert:
forall (R: ret_assert) (F: assert) ek vl,
proj_ret_assert (frame_ret_assert R F) ek vl =
seplog.sepcon (proj_ret_assert R ek vl) F.