proposition: Lemma discrete_stable_mult : forall A (c : nat -> U) (p : nat -> A), wretract c -> stable_mult (discrete c p).
proof: Proof. red; intros. repeat rewrite discrete_simpl; unfold fmult. apply Oeq_trans with (serie (fun k0 : nat => k * (c k0 * f (p k0)))); auto. apply serie_mult. apply wretract_le with c; auto. Qed.
imports: ALEA(Monads) ALEA(Utheory)