anchor.diff:          (unless (line-next line)
             (return nil))
           (push (make-fatstring "" 0) del-lines)
  -        (decf n (1+ (- (fat-length (line-fatstr line)) col)))
  +        (unless (eq n t)
  +          (decf n (1+ (- (fat-length (line-fatstr line)) col))))
           (decf (buffer-nlines buffer))
           (buffer-modify buffer)
           (setf (line-fatstr line)
  
positive.code:   (buffer-read-only-guard buffer)
    (let ((line (buffer-get-line buffer linum))
          (del-lines (list (make-fatstring "" 0))))
      (loop while (plusp n) do
        (cond
         ((<= n (- (fat-length (line-fatstr line)) col))
          (dolist (marker (buffer-markers buffer))
            (when (and (= linum (marker-linum marker))
                       (< col (marker-column marker)))
  
negative.code:     del-lines))
  
  (defun buffer-erase (buffer)
    (buffer-delete-char buffer 1 0 t)
    (let ((line (make-line nil nil "")))
      (setf (buffer-head-line buffer) line)
      (setf (buffer-tail-line buffer) line)
  