Theorem plusExactExpCanonic : forall c d p q : float, Fbounded b c -> Fbounded b d -> Fbounded b p -> Fbounded b q -> Closest b radix (c + d) p -> q = (c + d - p)%R :>R -> q <> 0%R :>R -> ex (fun r : float => ex (fun s : float => Fcanonic radix b s /\ Fbounded b r /\ s = p :>R /\ r = (c + d - s)%R :>R /\ Fexp r = Zmin (Fexp c) (Fexp d) :>Z /\ (Fexp r < Fexp s)%Z /\ (Fexp s <= Zsucc (Zmax (Fexp c) (Fexp d)))%Z)).