; my-append : (list-of α), (list-of α) -> (list-of α)
; return a list with the elements of `a` tacked on to the front of `b`
;
(define (my-append a b)
  (cond [(empty? a) b]
        [(cons? a)  (cons (first a) (my-append (rest a) b))]))


(check-expect (my-append '() '()) '())
(check-expect (my-append '() (list 1)) (list 1))
(check-expect (my-append '() (list 1 2 3)) (list 1 2 3))
(check-expect (my-append (list 1) '()) (list 1))
(check-expect (my-append (list 1 2 3) '()) (list 1 2 3))

(check-expect (my-append (list 1) (list 2)) (list 1 2))
(check-expect (my-append (list 1 2) (list 3)) (list 1 2 3))
(check-expect (my-append (list 1) (list 2 3)) (list 1 2 3))

(check-expect (my-append (list 1 2 3) (list 4 5 6)) (list 1 2 3 4 5 6))