proposition: Lemma ursubmxEsub : ursubmx = mxsub (lshift _) (@rshift _ _) A.
proof: Proof. by rewrite /ursubmx rsubmxEsub usubmxEsub -mxsub_comp. 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)