anchor.diff:               for q-row across q-table do
                (loop for x fixnum from 0 to 7
                      for val fixnum = (ash (svref block-row x) -3)
  -                   for qc fixnum = (svref q-row x) do
  +                   for qc fixnum = (aref q-row x) do
                      (setf (svref block-row x) (the fixnum (round val qc)))))
       '(loop for block-row across block
              for q-row across q-table do
              (loop for x fixnum from 0 to 7
                    for val fixnum = (ash (svref block-row x) -3)
                    for absval fixnum = (abs val)
  -                 for qc fixnum = (svref q-row x) do
  +                 for qc fixnum = (aref q-row x) do
                    (cond ((< absval (ash qc -1))
                           ;; you won't believe, but under LWW 4.1 such ugly hack gives
                           ;; very sufficient speedup
  
positive.code: (eval-when (:compile-toplevel :load-toplevel :execute)
  ;;; For ease of reference
  (defmacro dbref (data x y)
    `(the fixnum (svref (svref ,data ,y) ,x)))
  
  ;;; Integer arithmetic wrappers
  (defmacro plus (a b)
  
negative.code:                             &key (q-tabs +q-tables+) (sampling '((2 2)(1 1)(1 1))) (q-factor 64))
    (declare #.*optimize*
             (type fixnum ncomp h w q-factor)
             (type (array uint8 *) image))
    (when (= ncomp 1)
      (setq sampling '((1 1))))
    (let* ((wd (loop for entry in sampling maximize (first entry)))
  