>
> > If I use C-x C-t, the cursor goes down, while the line goes up. I cannot
> > move the line the second time.
>
> Which line?  Obviously one line is moving down if another is moving up.
> If you want point to move along with the upward-moving line rather than
> the downward-moving one, use C-- C-x C-t (and then C-x z z ... as needed).
>
> > And this only transposes the line, not move the line.
>
> What's the difference?
>
>
This is a good question. Please, can you write 2 lambda functions that
behaves exactly like the code below, and attach them to M-up , M-down ?

You should use only transpose-line, and none other function that deletes
text, like delete-and-extract-region, kill-line, etc.


(defun line-move-- (n)
  (if (> (point-max) (point-at-eol))
      (let ((column (current-column) )
            (line (delete-and-extract-region (point-at-bol) (1+
(point-at-eol)))))
        (forward-line n)
        (insert-string line)
        (backward-char)
        (move-to-column column) ) ) )

(define-key global-map [(meta up)]
  (lambda (&optional n)
    (interactive "P")
    (line-move-- (- (if (numberp n) n 1) ) ) ) )

(define-key global-map [(meta down)]
  (lambda (&optional n)
    (interactive "P")
    (line-move-- (if (numberp n) n 1) )  ) )

;;;;;

Using transpose-line , it is much direct to simulate line-move--down than I
did.