proposition: Lemma eq_mxblockP A_ B_ : (forall i j, A_ i j = B_ i j) <-> (\mxblock_(i, j) A_ i j = \mxblock_(i, j) B_ i j).
proof: Proof. by rewrite -mxblockP; split => + i j => /(_ i j); rewrite !mxblockK. 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 countalg finalg zmodp)