rewrite R.unsquash_squash.
simpl.
apply extensionality; intro l.
unfold compose; simpl; auto.
Qed.

Lemma make_rmap'':
forall n (f: AV.address -> resource) ,
AV.valid (fun l => res_option (f l)) ->
exists phi:rmap, level phi = n /\ resource_at phi = resource_fmap (approx n) oo f.