;; =================
;; Data definitions:

;; ListOfString is one of:
;;  - empty
;;  - (cons String ListOfString)
;; interp. a list of strings

(define LS0 empty)
(define LS1 (cons "a" empty))
(define LS2 (cons "a" (cons "b" empty)))
(define LS3 (cons "c" (cons "b" (cons "a" empty))))

#;
(define (fn-for-los los)
  (cond [(empty? los) (...)]
        [else
         (... (first los)
              (fn-for-los (rest los)))]))

;; Template rules used:
;; - one of: 2 cases
;; - atomic distinct: empty
;; - compound: (cons String ListOfString)
;; - atomic non-distinct: (first los) is  String
;; - self-reference: (rest los) is ListOfString

;; =================
;; Functions:

;; ListOfString -> ListOfString
;; adds "!" to every string in a ListOfString

(check-expect (yell empty) empty)
(check-expect (yell (cons "cat" empty)) (cons "cat!" empty))
(check-expect (yell (cons "cat"(cons "Nas" empty))) (cons "cat!"(cons "Nas!" empty)))


(define (yell los)
  (cond [(empty? los) empty]
        [else
         (...) ]))