proposition: Lemma scalar_mx0 : forall n, 0 %:M === @null_mx n n.
proof: Proof. by move=> n i j; rewrite/block_mx/pastemx/trmx/null_mx/addmx/oppmx/scalemx/scalar_mx/mulmx; case: eqP=> _; ring. Qed.
imports: ssreflect ssrbool ssrfun eqtype ssrnat seq choice fintype finfun bigops ssralg groups perm zmodp morphisms Ring RingClass bigopsClass Setoid Morphisms