(** **** Exercise: 3 stars  (bevalR)  *)
(** Write a relation [bevalR] in the same style as [aevalR], and prove that it is equivalent to [beval].*)
Inductive bevalR: bexp -> bool -> Prop :=
(* FILL IN HERE *)
.

Lemma beval_iff_bevalR : forall b bv,
bevalR b bv <-> beval b = bv.