#lang sicp

(define (fast-exp b n)
  ;(define (even?)); already defined by racket
  (define (actual b n a)
    (cond
      ((= n 0) a)
      ;((= n 1) a)
      ((even? n) (actual (* b b) (/ n 2) a))
      (else (actual b (- n 1) (* a b)))))
  (actual b n 1))