intros z m H H0.
case (Zle_or_lt 0 m); intros H1.
case (FboundedMboundPos z (Zabs m)); auto; try rewrite Zabs_eq; auto.
intros f (H2, H3); exists f; split; auto.
case (FboundedMboundPos z (Zabs m)); auto; try rewrite Zabs_eq_opp;
auto with zarith.
intros f (H2, H3); exists (Fopp f); split; auto with float.
rewrite (Fopp_correct radix); auto with arith; fold FtoRradix in |- *;
rewrite H3.
rewrite Ropp_Ropp_IZR; ring.
Qed.

Theorem FnormalPrecision :
forall p : float, Fnormal p -> Fdigit radix p = precision.