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 *)

(* Reroot Equation *)
Lemma field_at_data_at: forall t nf v p,
field_at t nf v p = data_at _ v (field_address t nf p).