anchor.diff:                                   (:back  extra-capacity)
                                    (t      (ash (ufixnum- new-capacity size) -1)))))
               (dotimes (i size)
  -              ;; this one is ignoring the resizable array in default cl --- performance comparison required?
  +              ;; guicho271828: this one is ignoring the resizable array in default cl --- performance comparison required?
  +              ;; cosmos72: some initial benchmarks on SBCL show that VECTOR* is significantly faster than adjustable CL arrays.
  +              ;;           The reason is VECTOR* compiles to highly optimized code on SBCL, not slowness of SBCL adjustable CL arrays.
  +              ;;           On most other Lisps, VECTOR* is much slower so I will probably provide a compile-time switch
  +              ;;           to implement VECTOR* on top of adjustable CL arrays.
                 (setf (aref new-data (ufixnum+ i new-start))
                       (aref old-data (ufixnum+ i old-start))))
               (setf <qdata>  new-data
  
positive.code:             (when (> required available)
                (let ((new-capacity
                       (if (<= old-capacity (truncate array-dimension-limit 2))
                           #+nil (* old-capacity 2)
                           (ash old-capacity 1) ;; twice the size
                           array-dimension-limit)))
                  (reserve (<deque>) deque
  
negative.code:              (asked-capacity (max new-capacity size))
               (extra-capacity (if (eq at :both)
                                   0
                                   (min (ash asked-capacity -2)
                                        (ufixnum- array-dimension-limit asked-capacity))))
               (new-capacity (ufixnum+ asked-capacity extra-capacity)))
              
  