proposition: Lemma map_mx_comp (f : R -> S) (g : S -> T) (M : 'M_(m, n)) : M ^ (g \o f) = (M ^ f) ^ g.
proof: Proof. by 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)