anchor.diff:                (unless (line-offset start-point 1)
                   (return)))))
   
  -@export
   (defun line-number-at-point (point)
     @lang(:jp "`point`の行番号を返します。")
     (point-linum point))
   
  -@export
   (defun point-column (point)
     @lang(:jp "`point`の行頭からの列幅を返します。")
     (let ((*tab-size* (variable-value 'tab-width :default point)))
  
positive.code:                      (point-line new-point)
                       (point-charpos new-point)))
  
  @export
  (defun line-start (point)
    @lang(:jp "`point`を行頭に移動します。")
    (setf (point-charpos point) 0)
    point)
  
  @export
  (defun line-end (point)
    @lang(:jp "`point`を行末に移動します。")
    (setf (point-charpos point)
          (line-length (point-line point)))
    point)
  
  @export
  (defun buffer-start (point)
    @lang(:jp "`point`をバッファの最初の位置に移動します。")
    (move-point point (buffer-start-point (point-buffer point))))
  
  @export
  (defun buffer-end (point)
    @lang(:jp "`point`をバッファの最後の位置に移動します。")
    (move-point point (buffer-end-point (point-buffer point))))
  
  @export
  (defun line-offset (point n &optional (charpos 0))
    @lang(:jp "`point`を`n`が正の数なら下に、負の数なら上に行を移動し、移動後の`point`を返します。
  `n`行先に行が無ければ`point`の位置はそのままでNILを返します。
  
negative.code:                        (line-char (point-line point)
                                    (point-charpos point)))))
  
  (defun line-string (point)
    @lang(:jp "`point`の行の文字列を返します。")
    (line-str (point-line point)))
  
  (defun text-property-at (point prop &optional (offset 0))
    @lang(:jp "`point`から`offset`ずらした位置の`prop`のプロパティを返します。")
    (%character-offset point offset
  