proposition: Lemma capmxT m1 m2 n (A : 'M_(m1, n)) (B : 'M_(m2, n)) : row_full B -> (A :&: B :=: A)%MS.
proof: Proof. rewrite -sub1mx => s1B; apply/eqmxP. by rewrite capmxSl sub_capmx submx_refl (submx_trans (submx1 A)). 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)