[ESS] How to improve ESS syntax high-lighting and shortcuts

[Richard M. Heiberger]

This is the comment.dwim from newcomment.el in GNU Emacs.
Does it work on Xemacs?  If so, you can bind it to the M-; key.


(defun comment-dwim (arg)
  "Call the comment command you want (Do What I Mean).
If the region is active and `transient-mark-mode' is on, call
  `comment-region' (unless it only consists of comments, in which
  case it calls `uncomment-region').
Else, if the current line is empty, insert a comment and indent it.
Else if a prefix ARG is specified, call `comment-kill'.
Else, call `comment-indent'."
  (interactive "*P")
  (comment-normalize-vars)
  (if (and mark-active transient-mark-mode)
      (comment-or-uncomment-region (region-beginning) (region-end) arg)
    (if (save-excursion (beginning-of-line) (not (looking-at "\\s-*$")))
	;; FIXME: If there's no comment to kill on this line and ARG is
	;; specified, calling comment-kill is not very clever.
	(if arg (comment-kill (and (integerp arg) arg)) (comment-indent))
      (let ((add (if arg (prefix-numeric-value arg)
		   (if (= (length comment-start) 1) comment-add 0))))
	;; Some modes insist on keeping column 0 comment in column 0
	;; so we need to move away from it before inserting the comment.
	(indent-according-to-mode)
	(insert (comment-padright comment-start add))
	(save-excursion
	  (unless (string= "" comment-end)
	    (insert (comment-padleft comment-end add)))
	  (indent-according-to-mode))))))