Definition field_at (t: type) (nf: list ident) (v: reptype (nested_field_type t nf)) (p: val) : Pred := data_at_rec (nested_field_type t nf) v (offset_val (nested_field_offset t nf) p).
Definition data_at (t: type) (v: reptype t) (p: val) : Pred := field_at t nil v p.
Definition field_address (t: type) (nf: list ident) (p: val) : val := offset_val (nested_field_offset t nf) p.
(* Ramification Premises for Nested Load/Store Rule *)

Lemma RP_mapsto: forall t nf u v p w0 w1,
legal_nested_field t nf ->
legal_type t ->
nested_field_type t nf = Tint ->
JMeq (proj_reptype t nf u) w0 ->
JMeq v w1 ->
data_at t u p |-- mapsto (field_address t nf p) w0 *
(mapsto (field_address t nf p) w1 -* data_at t (upd_reptype t nf u v) p).