fucking scholar

;; e)

;; (nheight nlist) consumes a nested list nlist and returns
;; the height corresponding to the maximum number of lists that
;; have been nested
;; nheight: Nested-Listof-Any -> Nat
;; Examples:
(check-expect (nheight empty) 1)
(check-expect (nheight '((1))) 2)

(define (nheight nlist)
  (nfoldr (lambda (x y) y)
          (lambda (x y) (max (+ x 1) y))
          1
          nlist))

;; Test:
(check-expect (nheight '((1) 2 ((3)))) 3)


;; f)

;; (prune nlist) consumes a nested list nlist and returns a
;; list where all empty nested lists have been removed
;; prune: Nested-Listof-Num -> Nest-Listof-Num
;; Examples:
(check-expect (prune '()) empty)
(check-expect (prune '(1 () 2)) '(1 2))

(define (prune nlist)
  (nfoldr (lambda (x y) (cons x y))
          (lambda (x y)
            (cond
              [(empty? x) (append y)]))
          empty
          nlist))

;; Tests:
(check-expect (prune '(1 2 3)) '(1 2 3))
(check-expect (prune '(1 () 3 () (()))) '(1 3))