(** Def 5 of (Rose) *)

Definition Mod2_e : Cobham :=
  Rec
    Zero
    (False_e 2)
    (One_e 2)
    (One_e 1).

Lemma PlusOneMinusMod2_correct : forall l, bs2nat (Sem PlusOneMinusMod2_e l) = bs2nat (hd nil l) + (1 - bs2nat (hd nil (tl l))) * mod2 (bs2nat (hd nil (tl (tl l)))).