d

;; d)

;; (nreverse nlist) consumes a Nested-Listof-Any nlist and reverses
;; every nested list
;; nreverse: Nested-Listof-Any -> Nested-Listof-Any
;; Examples:
(check-expect (nreverse (list 1 3 (list 7 9))) (list (list 9 7) 3 1))
(check-expect (nreverse empty) empty)

(define (nreverse nlist)
  (nfoldr (lambda (x y) (append y (list x)))
          (lambda (x y) (append y (list x)))
          empty
          nlist))

;; Test:
(check-expect (nreverse (list (list 1 2)(list 3 4))) (list (list 4 3)(list 2 1)))