;; list-append: list, list -> list
;; the function takes a list and returns
;; a new list which consists of all the elements
;; of the first list followed by all the elements
;; of the second list
;; Examples:
;; (list-append (list 5 6 7) (list 3 6 0)) -> (list 5 6 7 3 6 0)
;; (list-append empty (list 5 6 7)) -> (list 5 6 7)


(define (list-append list1 list2)
  (cond
    [(empty? list1) list2]
    [else (cons (first list1) (list-append (rest list1) list2))]
  )
)

(check-expect (list-append empty (list 5 6 7)) (list 5 6 7))
(check-expect (list-append (list 5 6 7) empty) (list 5 6 7))
(check-expect (list-append (list 5 6 7) (list 3 6 0)) (list 5 6 7 3 6 0))


;; list-reverse: list -> list
;; the function takes a list and returns a list
;; of the same elements, but in reverse order
;; Example:
;; (list-reverse (list 1 2 3 4 5)) -> (list 5 4 3 2 1)

(define (list-reverse a-list)
  (cond
    [(empty? a-list) empty]
    [else (list-append (list-reverse (rest a-list)) (list (first a-list)))] 
  )
)

(check-expect (list-reverse empty) empty)
(check-expect (list-reverse (list 3))  (list 3))
(check-expect (list-reverse (list 1 2 3 4 5)) (list 5 4 3 2 1))