proposition: Lemma submx0 m n (A : 'M_(m, n)) : (A <= (0 : 'M_n))%MS = (A == 0).
proof: Proof. by apply/idP/eqP=> [|->]; [apply: submx0null | apply: sub0mx]. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg finalg zmodp matrix)