fact: Definition cancel_sub prec xi yi := match xi, yi with | Ibnd xl xu, Ibnd yl yu => Ibnd (F.add_DN prec xl yu) (F.add_UP prec xu yl) | _, _ => Inan end.
imports: Coq(Bool Reals Psatz) Flocq(Raux) Stdlib Xreal Basic Sig Interval