anchor.diff:  (defparameter calc '(0))
   (defvar *text-field* nil)
   
  -(defun slidertest ()
  -  (loop for port in climi::*all-ports*
  -      do (destroy-port port))
  -  (setq climi::*all-ports* nil)
  +(defun sliderdemo ()
     (let ((frame (make-application-frame 'sliderdemo)))
       (run-frame-top-level frame)))
   
  
positive.code: 
  (defun find-text-field (frame)
    (first (member-if #'(lambda (gadget) (typep gadget 'text-field))
  		    (frame-panes frame))))
  
  (defmethod sliderdemo-frame-top-level ((frame application-frame)
  				       &key (command-parser 'command-line-command-parser)
  				       (command-unparser 'command-line-command-unparser)
  				       (partial-command-parser
  					'command-line-read-remaining-arguments-for-partial-command)
  				       (prompt "Command: "))
    (declare (ignore command-parser command-unparser partial-command-parser prompt))
    (setf *text-field* (find-text-field frame))
    (clim-extensions:simple-event-loop))
  
  (define-application-frame sliderdemo () ()
    (:panes
     (plus             :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "+"
  		     :activate-callback (queue-operator #'+))
     (dash             :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "-"
  		     :activate-callback (queue-operator #'-))
     (multiplicate     :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "*"
  		     :activate-callback (queue-operator #'*))
     (divide           :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "/"
  		     :activate-callback (queue-operator #'round))
     (result           :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "="
  		     :activate-callback #'do-operation)
     (one              :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "1"
  		     :activate-callback (queue-number 1))
     (two              :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "2"
  		     :activate-callback (queue-number 2))
     (three            :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "3"
  		     :activate-callback (queue-number 3))
     (four             :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "4"
  		     :activate-callback (queue-number 4))
     (five             :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "5"
  		     :activate-callback (queue-number 5))
     (six              :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "6"
  		     :activate-callback (queue-number 6))
     (seven            :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "7"
  		     :activate-callback (queue-number 7))
     (eight            :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "8"
  		     :activate-callback (queue-number 8))
     (nine             :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "9"
  		     :activate-callback (queue-number 9))
     (zero             :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "0"
  		     :activate-callback (queue-number 0))
    (screen            :text-field
  		     :value "0"
  		     :space-requirement (make-space-requirement :width 200 :height 50))
    (ac                :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "AC"
  		     :activate-callback #'initac)
    (ce                :push-button
  		     :space-requirement (make-space-requirement :width 50 :height 50)
  		     :label "CE"
  		     :activate-callback #'initce)
    (slider            :slider
  		     :value-changed-callback #'slide
  		     :min-value 0
  		     :max-value 100
  		     :value 0
  		     :normal +white+
  		     :highlighted +cyan+
  		     :pushed-and-highlighted +blue+))
  
    (:layouts
     (defaults (horizontally ()
  	        (vertically ()
  
negative.code:        (if (numberp last-item)
  	   (setf (car (last calc)) (+ (* 10 last-item) ,int))
  	   (setf calc (nconc calc (list ,int))))
         (setf (gadget-value *text-field*)
               (princ-to-string (first (last calc)))))))
  
  (defmacro queue-operator (operator)
    `(lambda (gadget)
  