(** * Power function *)
Section nat_to_ring.
Context {K : Ring}.
Definition nat_to_ring (n : nat) : K :=
sum_n_m (fun _ => one) 1 n.

(* Specifications: *)
Lemma nat_to_ring_O :
nat_to_ring O = zero.
Lemma nat_to_ring_Sn (n : nat) :
nat_to_ring (S n) = plus (nat_to_ring n) one.