anchor.diff:    (make-q :compare-fn compare-fn
             :set-index-fn set-index-fn
             :get-index-fn get-index-fn
  -          :items (make-array size :element-type element-type :fill-pointer 0 :adjustable t)))
  +          :items (make-array size :fill-pointer 0 :adjustable t)))
   
   (defun queue-empty-p (q)
     "Are there no items in the queue?"
  
positive.code:   ()
    (:documentation "Signaled when an operation depends on an item that was not found in the queue."))
  
  ;;;; Basic Operations on Queues
  
  (defconstant +not-in-queue+ -1)
  
  (defstruct q
    (compare-fn nil :type function)
  
negative.code:   (get-index-fn nil :type function)
    (items nil :type array))
  
  (defun make-empty-queue (compare-fn set-index-fn get-index-fn &key (size 100))
    "Return a new empty queue.
  
  compare-fn is a function that takes two arguments and returns a true
  