(** Composed operations *)
Section Operations_fct.
Context {K : AbsRing} {U V : NormedModule K}.

Lemma ex_filterdiff_minus_fct {F} {FF : Filter F} (f g : U -> V) :
ex_filterdiff f F -> ex_filterdiff g F ->
ex_filterdiff (fun u => minus (f u) (g u)) F.