Hint Rewrite @evalCR_step: Recurrence.
(** Now that we know what happens at 0 and inductive case, we're done *)
Opaque evalCR.

(* Specifications: *)
(** Lemma 16 *)
Lemma add_const_to_CR:
forall `{Ring R} (r c0: R) (cr: CR) (n: nat),
r + ((recurCR c0 plus cr) # n) =
((recurCR (c0 + r) plus cr) # n).