Problem$^a$ 1.  Take a look at these structure and data definitions:

(define-struct message (slot cont))
;; An Message is one of: 
;; -- Symbol
;; -- String 
;; -- (make-message NaturalNumber String)

Answer the following questions in this context:

1. Write down the constructor and predicate that the structure definition introduces:

   Solution [PT 2]

   make-message message? 

2. Write down three distinct data examples, one per clause:

   Solution [PT 1]

       'hello    "world"      (make-message 10 'hello)
   

3. Write down the template for a function that consumes a Message:

   ;; program : Message -> ???
   

   Solution [PT 2: 1 for three cond lines, 1 for selector expressions]

   (define (program e)
     (cond
       [(symbol? e) ...]
       [(string? e) ...]
       [else (message-slot e) ... (message-cont e)]))
   

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