intros P p H' H'0 H'1 H'2 q H'3 H'4 H'5.
apply FinductNegAux with (p := p) (x := (Fweight p - Fweight q)%Z); auto.
cut (Fweight q <= Fweight p)%Z; [ auto with zarith | idtac ].
apply FweightZle; auto with float.
Qed.

Theorem radixRangeBoundExp :
forall p q : float,
Fcanonic radix b p ->
Fcanonic radix b q ->
(0 <= p)%R ->
(p < q)%R -> (q < radix * p)%R -> Fexp p = Fexp q \/ Zsucc (Fexp p) = Fexp q.