;; map is a predefined function that allows you to apply a function to 
;; every element of a list and create a new list out of
;; the results.

;; number -> number
;; computes square of x
(define (square x) (* x x))

(check-expect (map square (list 1 2 5 8 0 -3 -4)) (list 1 4 25 64 0 9 16))


(check-expect (map length (list (list 1 2 3) (list 'a 'b 'c 'd) empty)) 
              (list 3 4 0))

(map even? (list 1 2 5 8 0 -3 -4))
;; what do you expect to be returned?


;; use the test examples above to write your own definition of map,
;; call it map1
;; Don't forget the contract!