proposition: Lemma eigenspaceP a m (W : 'M_(m, n)) : reflect (W *m g = a *: W) (W <= eigenspace a)%MS.
proof: Proof. by rewrite sub_kermx mulmxBr subr_eq0 mul_mx_scalar; apply/eqP. 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)