intros p H; case H; auto.
intros H1 H2; case H2; auto.
Qed.
Hint Resolve FsubnormalFbounded FsubnormalBound FsubnormalFexp: float.

Theorem FsubnormFopp : forall p : float, Fsubnormal p -> Fsubnormal (Fopp p).
intros p H'; repeat split; simpl in |- *; auto with zarith float.