Section FinDepTheory.
Variables (aT : finType) (rT : aT -> finType).
Notation fT := {dffun forall x : aT, rT x}.

Lemma card_family (F : forall x, pred (rT x)) :
#|(family F : simpl_pred fT)| = foldr muln 1 [seq #|F x| | x : aT].