(** Def 5 of (Rose) *)

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

Lemma PlusOneMinus'_correct : forall l, hd nil (tl l) = nil \/ bs2nat (hd nil (tl l)) <> 0 -> bs2nat (Sem PlusOneMinus'_e l) = bs2nat (hd nil l) + (1 - bs2nat (hd nil (tl l))).