Definition CPToList {T:Type} {n:nat} (cp : cartesianPower T n) : list T.Definition InCP {T:Type} {n:nat} p (cp : cartesianPower T n) := In p (CPToList cp).

Lemma InCPOK {T:Type} {n:nat} : forall p (cp : cartesianPower T (S (S n))), InCP p cp <-> ((p = headCP cp) \/ InCP p (tailCP cp)).