proposition: Lemma mxdirectE m n (S : mxsum_expr m n) : mxdirect (unwrap S) = (\rank (unwrap S) == unwrap (mxsum_rank S)).
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 finalg zmodp matrix)