Opaque MultTwoPowerLength'_e.
Definition MultTwoPowerLength_e : Cobham :=
Comp 2 MultTwoPowerLength'_e [Proj 2 1; Proj 2 0].

Lemma MultTwoPowerLength_correct : forall l,
bs2nat (Sem MultTwoPowerLength_e l) =
bs2nat (hd nil l) * power 2 (length (hd nil (tl l))).