proposition: Lemma subring_closedM : subring_closed -> smulr_closed.
proof: Proof. by case=> S1 SB SM; split; rewrite ?(zmod_closedN (subring_closedB _)). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)