Definition Fulp (p : float) :=
  powerRZ radix (Fexp (Fnormalize radix b precision p)).

Theorem RoundMSBmin : forall (P : R -> float -> Prop) (p q : float), RoundedModeP b radix P -> P p q -> p <> 0%R :>R -> (- dExp b <= MSB radix p)%Z -> (MSB radix p <= MSB radix q)%Z.