fact: Parameter sub_UP_correct : forall p x y, valid_ub x = true -> valid_lb y = true -> (valid_ub (sub_UP p x y) = true /\ le_upper (Xsub (toX x) (toX y)) (toX (sub_UP p x y))).
imports: Coq(ZArith Reals) Flocq(Zaux Raux) Xreal Basic