(define (front-ptr queue) (car queue))
	(define (rear-ptr queue) (cdr queue))
	(define (set-front-ptr! queue item) (set-car! queue item))
	(define (set-rear-ptr! queue item) (set-cdr! queue item))
	(define (empty-queue? queue) (null? (front-ptr queue)))
	(define (make-queue) (cons '() '()))

	(define (front-queue queue)
	  (if (empty-queue? queue)
	      (error "FRONT called with an empty queue" queue)
	      (car (front-ptr queue))))

	(define (insert-queue! queue item)
	  (let ((new-pair (cons item '())))
	    (cond ((empty-queue? queue)
	           (set-front-ptr! queue new-pair)
	           (set-rear-ptr! queue new-pair)
	           queue)
	          (else
	           (set-cdr! (rear-ptr queue) new-pair)
	           (set-rear-ptr! queue new-pair)
	           queue))))
	          
	(define (delete-queue! queue)
	  (cond ((empty-queue? queue)
	         (error "DELETE! called with an empty queue" queue))
	        (else
	         (set-front-ptr! queue (cdr (front-ptr queue)))
	         queue)))

; this is the procedure of printing queue
	(define (print-queue queue)
	  (display (car queue)))


	(define q1 (make-queue))

	(insert-queue! q1 'a)

	(insert-queue! q1 'b)

	(print-queue q1)

	(delete-queue! q1)
	(print-queue q1)
	(delete-queue! q1)
	(print-queue q1)