Section BigSum.
Variable I : finType.
Implicit Type P : pred I.
End BigSum.
(* Intersection *)
End BigCap.

Lemma dimv_leq_sum I r (P : pred I) (Us : I -> {vspace vT}) :
\dim (\sum_(i <- r | P i) Us i) <= \sum_(i <- r | P i) \dim (Us i).