unfold Dcompare in |- *; simpl in |- *; intros;
rewrite (Zmin.Zmin_plus (Dexp x) (Dexp y) n).
do 2 rewrite BinInt.Zminus_plus_simpl_r.
reflexivity.
Qed.

Lemma eq_Deq : forall x y : diadic, x = y -> Deq x y.
intros; rewrite H; unfold Deq in |- *; unfold Dcompare in |- *;
apply Zcompare.Zcompare_eq_case; trivial.