proposition: Lemma eq_mxsub m' n' f f' g g' : f =1 f' -> g =1 g' -> @mxsub m' n' f g =1 mxsub f' g'.
proof: Proof. by move=> eq_f eq_g A; apply/matrixP => i j; rewrite !mxE eq_f eq_g. 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)