anchor.diff:          (delete-point mark)))))
   
   (defun insert-buffer (point buffer)
  +  "`point`の位置に`buffer`内のテキストを挿入します。
  +`insert-string`との違いは`buffer`内のテキストプロパティも反映することです。"
     (loop :for line := (point-line (buffer-start-point buffer)) :then (line-next line)
           :while line
           :do (insert-string point (line-str line))
  
positive.code:           nil))))
  
  (defun point-bytes (point)
    (with-point ((point point))
      (let ((nbytes 0))
        (incf nbytes
  
negative.code:                (line-offset (buffer-end point) (- line-number nlines)))))))
  
  (defun check-marked ()
    "`current-buffer`内でマークが置かれていなければ`editor-error`を起こします。"
    (unless (buffer-mark (current-buffer))
      (editor-error "Not mark in this buffer")))
  
  