proposition: Lemma map2_row i : map2_mx (row i A) (row i B) = row i (map2_mx A B).
proof: Proof. by apply/rowP=> 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)