proposition: Lemma smulr_closedM : smulr_closed -> mulr_closed S.
proof: Proof. by case=> SN1 SM; split=> //; rewrite -[1]mulr1 -mulrNN SM. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)