proposition: Lemma mxdirectP n (S : proper_mxsum_expr n) : reflect (\rank S = proper_mxsum_rank S) (mxdirect S).
proof: Proof. exact: eqnP. 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)