fact: Definition map2_mx m n (A : 'M_(m, n)) (B : 'M_(m, n)) := \matrix[map2_mx_key]_(i, j) f (A i j) (B i j).
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)