sort rectangle

(defun sort-rectangle (prefix)
  "Sort the text of a rectangle.

Has the effect of sorting in place."
  (interactive "p")
  (when-let ((_ (region-active-p))
             (anchor (region-beginning)))
    (kill-rectangle anchor (region-end))
    (with-temp-buffer
     (yank-rectangle)
     (let ((start (point-min))
           (stop  (point-max)))
       (sort-lines (= prefix 4) start stop)
       (kill-rectangle start stop)))
    (goto-char anchor)
    (yank-rectangle)))