intros x y H'; case (Zle_or_lt x y); auto; intros ZH; Contradict H'.
apply Rgt_not_le; red in |- *; apply oneExp_lt; auto.
Qed.
Definition Fdigit (p : float) := digit radix (Fnum p).
Definition Fshift (n : nat) (x : float) :=
Float (Fnum x * Zpower_nat radix n) (Fexp x - n).

Theorem sameExpEq : forall p q : float, p = q :>R -> Fexp p = Fexp q -> p = q.
intros p q; case p; case q; unfold FtoR in |- *; simpl in |- *.