proposition: Lemma comm_mxE (R : ringType) (n : nat) : @comm_mx R n.+1 = @GRing.comm _.
proof: Proof. by []. 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)