proposition: Lemma rsubmxEsub : rsubmx = colsub (@rshift _ _).
proof: Proof. by rewrite /rsubmx /mxsub !unlock. 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)