Ltac inv H := (apply join_YES_pfullshare1 in H || apply join_YES_pfullshare2 in H || idtac);
                  (inversion H; clear H; subst).Definition empty_rmap' : rmap'.Definition empty_rmap (n:nat) : rmap := R.squash (n, empty_rmap').

Lemma approx_FF: forall n, approx n FF = FF.