;; file-handler : file -> ?
;(define file-handler
;  (lambda (file)
;  >>>TO DO: complete the template for files.
;  (What are the the steps of writing the template?)
;  (Be sure to refer back to the data definition,
;  since the shape of the data determines the shape of the template.)










;;;;;;;;;;;;;;
;; Provided for you:

;; lof-handler : list_of_file -> ?
;(define lof-handler
;  (lambda (los)
;    (cond [(empty? lof)
;           ...]
;          [else
;           ... (file-handler (first lof))
;           ... (lof-handler (rest lof))
;           ...])))

;; los-handler : list_of_symbol -> ?
;(define los-handler
;  (lambda (los)
;    (cond [(empty? los)
;           ...]
;          [else
;           ... (first los)
;           ... (los-handler (rest los))
;           ...])))


;; contains?: symbol, list_of_symbol --> bool
;;
(define contains?
  (lambda (target los)
    (cond [(empty? los)   #f]
          [else
           (or (eq? target (first los))
               (contains? target (rest los)))])))

; Tests:
  (contains? 'pears empty)
= #f

  (contains? 'pears   (list 'pears))
= #t

  (contains? 'peaches (list 'pears))
= #f


  (contains? 'pears   (list 'four 'score 'and 'twenty 'pears 'ago))
= #t

  (contains? 'peaches (list 'four 'score 'and 'twenty 'pears 'ago))
= #f