proposition: Lemma addvC : commutative addV.
proof: Proof. by move=> U V; apply/vs2mxP; rewrite !vs2mxD addsmxC submx_refl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)