proposition: Lemma ex_filterdiff_opp_fct {F} {FF : Filter F} (f : U -> V) : ex_filterdiff f F -> ex_filterdiff (fun t => opp (f t)) F.
proof: Proof. intros [lf Df]. eexists. apply filterdiff_opp_fct ; eassumption. Qed.
imports: Coq(Reals Psatz ssreflect) Rcomplements Rbar Lim_seq Iter Hierarchy Continuity Equiv