anchor.diff:    (delete-char)
     (buffer-insert-char
      (current-buffer)
  -   (window-current-linum)
  -   (window-current-charpos)
  +   (current-linum)
  +   (current-charpos)
      c))
   
   (defun count-indent ()
  
positive.code:   (let ((buffer (current-buffer)))
      (when (buffer-check-marked buffer)
        (psetf
         (window-current-linum) (marker-linum (buffer-mark-marker buffer))
         (window-current-charpos) (marker-charpos (buffer-mark-marker buffer))
         (marker-linum (buffer-mark-marker buffer)) (window-current-linum)
         (marker-charpos (buffer-mark-marker buffer)) (window-current-charpos))
        (assert (<= 0 (window-current-charpos)))
        t)))
  
  (defun following-char ()
    (buffer-get-char (current-buffer)
                     (window-current-linum)
                     (window-current-charpos)))
  
  (defun preceding-char ()
    (cond
     ((bobp)
      nil)
     ((bolp)
      (buffer-get-char (current-buffer)
                       (1- (window-current-linum))
                       (buffer-line-length (current-buffer)
                                           (1- (window-current-linum)))))
     (t
      (buffer-get-char (current-buffer)
                       (window-current-linum)
                       (1- (window-current-charpos))))))
  
  (defun char-after (&optional (n 0))
    (if (zerop n)
  
negative.code:   (when (minusp column) (setq column 0))
    (let* ((old-column (current-column))
           (old-indent-string
             (save-excursion
              (region-string (progn (beginning-of-line) (current-point))
                             (progn (back-to-indentation) (current-point)))))
           (new-indent-string
             (if (get-bvar :indent-tabs-mode :default t)
                 (multiple-value-bind (div mod)
                     (floor column *tab-size*)
                   (concatenate 'string
                                (make-string div :initial-element #\tab)
                                (make-string mod :initial-element #\space)))
                 (make-string column :initial-element #\space))))
      (cond ((string/= old-indent-string new-indent-string)
             (beginning-of-line)
             (delete-char (length old-indent-string) t)
  