Variables g : BC.
Hypothesis g_inf  : arities g = ok_arities 1 (sl - 1).
Definition f'_nil := BC_dummies 1 1 2 (sl - 1) g.

(* Specifications: *)
Lemma f'_nil_inf : arities f'_nil = ok_arities 2 (S sl).
Opaque f'_nil.