proposition: Lemma mxE k F : matrix_of_fun k F =2 F.
proof: Proof. by move=> i j; rewrite unlock /fun_of_matrix /= ffunE. 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)