Notation cps T := ((T -> fF) -> fF).Definition ret T1 : T1 -> cps T1 := fun x k => k x.Definition bind T1 T2 (x : cps T1) (f : T1 -> cps T2) : cps T2 :=
  fun k => x (fun x => f x k).End ClosedFieldQE.Definition cpsif T (c : fF) (t : T) (e : T) : cps T :=
  fun k => GRing.If c (k t) (k e).Notation eval := GRing.eval.Notation rterm := GRing.rterm.Notation qf_eval := GRing.qf_eval.Definition rpoly (p : polyF) := all (@rterm F) p.Definition qf_red_cps T (x : cps T) (y : _ -> T) :=
   forall e k, qf_eval e (x k) = qf_eval e (k (y e)).Definition qf_cps T D (x : cps T) :=
  forall k, (forall y, D y -> qf (k y)) -> qf (x k).

Lemma isnull_qf (p : polyF) : rpoly p -> qf_cps xpredT (isnull p).