Definition lastCP {T:Type} {n:nat} (cp : cartesianPower T (S n)) : T.
Definition tailCPbis {T:Type} {n:nat} m1 m2 (cp : cartesianPower T m1) :
(S (S n)) = m1 -> (S n) = m2 -> (cartesianPower T m2).

Lemma consHeadCPOK {T:Type} {n:nat} :
forall (cp : cartesianPower T (S (S n))),
cp = consHeadCP (headCP cp) (tailCP cp).