My emacs configuration has grown up pretty big over the years and I have lot of useful stuff for me there but if I have two functions it probably would have been those ones.
Define C-x UP and C-x DOWN to move the current line or down keeping the cursor at the right place :
;Down/UP the current line
(global-set-key '[(control x) (up)] 'my-up-line)
(global-set-key '[(control x) (down)] 'my-down-line)
(defun my-down-line()
(interactive)
(let ((col (current-column)))
(forward-line 1)
(transpose-lines 1)
(forward-line -1)
(forward-char col)
)
)
(defun my-up-line()
(interactive)
(let ((col (current-column)))
(transpose-lines 1)
(forward-line -2)
(forward-char col)
)
)