proposition: Lemma mull_fun_is_scalable : scalable (a \*o f).
proof: Proof. by move=> k x /=; rewrite linearZ scalerAr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)