anchor.diff:  (deftype sint16-array () '(simple-array sint16 (*)))
   (deftype sint16-2d-array () '(simple-array sint16-array (*)))
   
  +(deftype uint16 () '(unsigned-byte 16))
  +(deftype uint16-array () '(simple-array uint16 (*)))
  +(deftype uint16-2d-array () '(simple-array uint16-array (*)))
  +
   (deftype fixnum-array () '(simple-array fixnum (*)))
   (deftype fixnum-2d-array () '(simple-array fixnum-array (*)))
   
  
positive.code:                 for cx fixnum = (minus xd dx)
                  for cy fixnum = (minus yd dy) do
                  (loop for i fixnum from 0 below ncomp do
                        (setf (u8ref (aref outbuf i) cx cy)
                              (minus (aref inbuf (plus pos i)) 128)))))
      (values xend yend)))
  
  
negative.code: ;;; ANSI Common Lisp (mostly) baseline JPEG encoder/decoder implementation
  ;;; Copyright [c] 1999,2015,2016 Eugene Zaikonnikov <eugene@funcall.org>
  ;;;               
  ;;; This software is distributed under the terms of BSD-like license
  