proposition: Lemma subid_addC m n (I : 'cV[R]_m) (J : 'cV[R]_n) : (I +i J <= J +i I)%IS.
proof: Proof. apply/subidP; exists (block_mx 0 1%:M 1%:M 0). by rewrite mul_block_col !(mul0mx,mul1mx) addr0 add0r. 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