Opaque succ_e.
(** * Addition  - arities: (1,1) *)
Definition plus_e : BC :=
rec (proj 0 1 0)
(comp 1 2 succ_e nil ((proj 1 2 1) :: nil))
(comp 1 2 succ_e nil ((proj 1 2 1) :: nil)).

Lemma plus_correct :
forall m n, length (sem plus_e [m] [n]) = length m + length n.