proposition: Lemma eq_in_map_mx (g f : R -> S) (M : 'M_(m, n)) : (forall i j, f (M i j) = g (M i j)) -> M ^ f = M ^ g.
proof: Proof. by move=> fg; apply/matrixP => i j; rewrite !mxE. 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)