proposition: Lemma genmxE m n (A : 'M_(m, n)) : (<<A>> :=: A)%MS.
proof: Proof. by rewrite unlock; apply/eqmxP; case/andP: (chooseP (genmx_witnessP 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)