Definition field_address t gfs p :=
  if (field_compatible_dec t gfs p)
  then offset_val (nested_field_offset t gfs) p
  else Vundef.Definition field_address0 t gfs p :=
  if (field_compatible0_dec t gfs p)
  then offset_val (nested_field_offset t gfs) p
  else Vundef.

Lemma nested_field_array_offset_in_range: forall t gfs lo hi, legal_nested_field0 t (ArraySubsc lo :: gfs) -> legal_nested_field0 t (ArraySubsc hi :: gfs) -> complete_legal_cosu_type t = true -> 0 <= nested_field_offset t (ArraySubsc lo :: gfs) /\ nested_field_offset t (ArraySubsc lo :: gfs) + sizeof (nested_field_array_type t gfs lo hi) <= sizeof t.