e.v0

  ;; Number Nat -> Number
  ;; compute e to the x to the n-th approximation 
  (define (e.v0 x n)
    (cond
      [(zero? n) 1]
      [else (+ (e.v0 x (sub1 n)) (/ (expt x n) (! n)))]))

  ;; where
  ;; ! : Nat -> Nat 
  (define (! n) (if (= n 0) 1 (* n (! (sub1 n)))))

  ;; TEST
  (=~ (e.v0 1 10) e .01)

Solution:

  ;; [PTS 3: for build-list, foldr, and correctness]
  (define (e.v1 x n)
    (foldr + 0 
      (build-list n (lambda (i) (/ (expt x i) (! i))))))