fact: Definition mxring m n (R : 'A_(m, n)) := left_mx_ideal R R && has_mxring_id R.
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)