proposition: Lemma subv_add U V W : (U + V <= W)%VS = (U <= W)%VS && (V <= W)%VS.
proof: Proof. by rewrite /subV vs2mxD addsmx_sub. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)