(check-expect (add-lists '(1 1) '(-1 -1)) '(0 0))
(check-expect (add-lists '(1 2 3) '(4 5 6))
              '(5 7 9))
(check-expect (add-lists (build-list 10 identity)
                         (reverse (build-list 10 identity)))
              (build-list 10 (lambda (x) 9)))

(check-error (add-lists '(1 2 3) '(4 5)) "length mismatch")
(check-error (add-lists '(1 2) '(3 4 5)) "length mismatch")

(check-expect (map2 cons '(1 2 3) '(() (3) (4)))
              '((1) (2 3) (3 4)))
(check-expect (map2 string-append
                    '("hello" "it is ") '(" world" "wednesday"))
              '("hello world" "it is wednesday"))