Opaque Div2_e.
(** Def 5 of (Rose) *)
Definition Mod2_e : Cobham :=
Rec
Zero
(False_e 2)
(One_e 2)
(One_e 1).

Lemma Mod2_correct : forall l,
bs2nat (Sem Mod2_e l) = mod2 (bs2nat (hd nil l)).