proposition: Lemma dimv_disjoint_sum U V : (U :&: V = 0)%VS -> \dim (U + V) = (\dim U + \dim V)%N.
proof: Proof. by move=> dxUV; rewrite -dimv_sum_cap dxUV dimv0 addn0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)