Opaque DivTwoPower_e.
(** Def 15 of (Rose) *)
Definition DivDivTwoPower_e : Cobham :=
Comp 3 DivTwoPower_e [Proj 3 0; Comp 3 DivTwoPower_e [Proj 3 1; Proj 3 2] ].

Lemma DivDivTwoPower_correct : forall l,
Sem DivDivTwoPower_e l =
skipn (length (nth 1 l nil) - length (nth 2 l nil)) (nth 0 l nil).