Opaque PlusOneMinus'_e.
Definition PlusOneMinus_e : Cobham :=
Comp 2 PlusOneMinus'_e [Proj 2 0; Comp 2 Normalize_e [Proj 2 1] ].

Lemma PlusOneMinus_correct : forall l,
bs2nat (Sem PlusOneMinus_e l) = bs2nat (hd nil l) + (1 - bs2nat (hd nil (tl l))).