Definition identity_rmap' : R.rmap' := exist valid (fun _: AV.address => R.NO) AV.valid_empty.Definition identity_rmap (n:nat) : rmap := R.squash (n, identity_rmap').

Lemma approx_approx' n n' x : (n' >= n)%nat -> approx n (approx n' x) = approx n x.