intros p q H' H'0 H'1.
apply FtoREqInv2 with (radix := radix); auto.
generalize H' H'0; unfold Fsubnormal in |- *; auto with zarith.
Qed.

Theorem FsubnormalLt :
forall p q : float,
Fsubnormal p -> Fsubnormal q -> (p < q)%R -> (Fnum p < Fnum q)%Z.