proposition: Lemma subidMl m n p (I : 'cV[R]_m) (J : 'cV[R]_n) (D : 'M_(p, _)) : (I <= J)%IS -> (D *m I <= J)%IS.
proof: Proof. by move=> /subidP [I' ->]; apply/subidP; exists (D *m I'); rewrite mulmxA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice fingroup) mathcomp(matrix bigop zmodp mxalgebra poly) ssrcomplements