proposition: Lemma memmx_map m n A (E : 'A_(m, n)) : (A^f \in E^f)%MS = (A \in E)%MS.
proof: Proof. by rewrite -map_mxvec map_submx. 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 finalg zmodp matrix)