intros x y H' H'0 H'1; unfold FNPred in |- *.
replace (FtoRradix x) with (FtoRradix (Fnormalize radix b precision x)).
apply FPredProp; auto with float.
unfold FtoRradix in |- *; repeat rewrite FnormalizeCorrect; auto.
unfold FtoRradix in |- *; repeat rewrite FnormalizeCorrect; auto.
Qed.

Theorem FPredSuc :
forall x : float,
Fcanonic radix b x -> FPred (FSucc b radix precision x) = x.