anchor.diff:          collecting (mem-aref foreign-array type i)))
   
   @export
  -(defun print-foreign-array (foreign-array size type &key (step 1))
  +(defun print-foreign-array (foreign-array size type &key (step 1) (index nil))
     (loop for i from 0 below size by step
  -        do (format t "~a, ~a~%" i (mem-aref foreign-array type i))))
  +        do (let ((value (mem-aref foreign-array type i)))
  +             (if index
  +                 (format t "~a, ~a~%" i value)
  +                 (format t "~a~%" value)))))
   
   @export
   (defun device-memory-to-simple-array (command-queue device size type &key (step 1))
  
positive.code:                          0
                           (* (foreign-type-size type) size)
                           foreign-array)
      (print-foreign-array foreign-array size type :step step)))
  
negative.code:     result))
  
  @export
  (defun print-device-memory (command-queue device size type &key (step 1) (index nil))
    (with-foreign-objects ((foreign-array type size))
      (enqueue-read-buffer command-queue
                           device
  