anchor.diff:     (eight    (make-button "8" (queue-number 8)))
      (nine     (make-button "9" (queue-number 9)))
      (zero     (make-button "0" (queue-number 0)))
  -   (screen   :text-field :value "0")
  +   (screen   :text-field :value "0" :text-style *calculator-text-style*)
      (ac       (make-button "AC" #'initac))
      (ce       (make-button "CE" #'initce)))
   
  
positive.code:          (vertically (:width 150 :max-width 500)
             (setf text-field screen)
             (horizontally (:height 50) ac ce)
             (tabling ()
               (list one two plus)
               (list three four dash)
               (list five six multiply)
  
negative.code:   (make-pane 'push-button-pane
  	     :label label
  	     :activate-callback operator
               :text-style *calculator-text-style*
  	     :width width :height height
  	     :max-width  max-width :min-width min-width
  	     :max-height max-height :min-height min-height))
  