1 665c255d 2023-08-04 jrmu ;; Exercise 3.22.  Instead of representing a queue as a pair of pointers, we can build a queue as a procedure with local state. The local state will consist of pointers to the beginning and the end of an ordinary list. Thus, the make-queue procedure will have the form
 2 665c255d 2023-08-04 jrmu 
 3 665c255d 2023-08-04 jrmu (define (make-queue)
 4 665c255d 2023-08-04 jrmu   (let ((front-ptr ...)
 5 665c255d 2023-08-04 jrmu         (rear-ptr ...))
 6 665c255d 2023-08-04 jrmu     <definitions of internal procedures>
 7 665c255d 2023-08-04 jrmu     (define (dispatch m) ...)
 8 665c255d 2023-08-04 jrmu     dispatch))
 9 665c255d 2023-08-04 jrmu 
10 665c255d 2023-08-04 jrmu ;; Complete the definition of make-queue and provide implementations of the queue operations using this representation.