proposition: Lemma map2_mxC {opm : Monoid.com_law idm} : commutative (@map2_mx _ _ _ opm m n).
proof: Proof. by move=> A B; apply/matrixP=> i j; rewrite !mxE Monoid.mulmC. 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)