Re: how to deal with comment in a new lang mode

[Xah <xahlee@gmail.com>]

Xah Lee wrote:
> > when writing a new language mode, how can one make comment-dwim work?
>
> > i can of course code my own functions dealing with comments, but i
> > think it is better to use the facilities provided in newcomment.el?
> > ...
> > any advice apprecated for dealing with comments in a new lang mode.

Kevin Rodgers wrote:
> I can't address your question, but I can suggest a minor simplification
> of your current implementation:
>
> (defun xlsl-comment-dwim (arg)
>    (interactive "*P")
>    (let ((comment-start "// ")
>          (comment-end ""))
>      (comment-dwim arg)))
>
> This is also has the advantage of restoring the original binding of
> the comment-start and comment-end variables, even if comment-dwim
> signals an error.

Thanks, it did help.

i haven't tested extensively, but looks like the above is all i need.
My previous problem of comment-dwim not doing any commenting/
uncommenting when on a line such as:
“;; this and that.”
while the cursor on the line, is the consistant behavior of comment-
dwim.

Not sure i liked the behavior of comment-dwim... i haven't decided
yet, but it seems too smart or quite complex. For now i decided to
experiment since it's not too difficult.

;; implementation using “newcomment.el”. I don't like comment-dwim's
behavior. Its too “smart/complex”. In particular, when there's no
active region and current line is a comment, it doesn't do anything
except moving cursor.
;; (defun xlsl-comment-dwim (arg)
;;    (interactive "*P")
;;    ;; (require 'newcomment)
;;    (let ((comment-start "// ")
;;          (comment-end ""))
;;      (comment-dwim arg)))

;; implementation not using “newcomment.el”.
(defun xlsl-comment-dwim ()
  "Comment or uncomment the current line or text selection."
  (interactive)
  ;; If there's no text selection, comment or uncomment the line
depending whether the WHOLE line is a comment. If there is a text
selection, using the first line to determine whether to comment/
uncomment.
  (let (p1 p2)
    (if (and transient-mark-mode mark-active)
        (save-excursion
          (setq p1 (region-beginning) p2 (region-end))
          (goto-char p1)
          (if (wholeLineIsCmt-p)
          (xlsl-uncomment-region p1 p2)
          (xlsl-comment-region p1 p2)
          ))
      (progn
        (if (wholeLineIsCmt-p)
            (xlsl-uncomment-current-line)
          (xlsl-comment-current-line)
          ))
      )
    ))

(defun wholeLineIsCmt-p ()
  (save-excursion
      (move-beginning-of-line 1)
      (looking-at "[ \t]*//")
      )
 )

(defun xlsl-comment-current-line ()
  (interactive)
  (move-beginning-of-line 1)
  (insert "//")
  )

(defun xlsl-uncomment-current-line ()
  "Remove the string “//” in the beginning of current line."
  (interactive)
  (when (wholeLineIsCmt-p)
    (move-beginning-of-line 1)
    (search-forward "//")
    (delete-backward-char 2)
    )
  )

(defun xlsl-comment-region (p1 p2)
  "Add “//” to the beginning of each line of selected text."
  (interactive "r")
  (let ((deactivate-mark nil))
    (save-excursion
      (goto-char p2)
      (while (>= (point) p1)
        (xlsl-comment-current-line)
        (previous-line)
        )
      )
    )
  )

(defun xlsl-uncomment-region (p1 p2)
  "Remove “//” in the beginning of each line of selected text."
  (interactive "r")
  (let ((deactivate-mark nil))
    (save-excursion
      (goto-char p2)
      (while (>= (point) p1)
        (xlsl-uncomment-current-line)
        (previous-line)
        )
      )
    )
  )

took me about 3 hours. Coding this i realized there's some details,
more complex than i originally thought but still not much work.
Possibly down the road i'll go back to basing it on “newcomment.el”.

PS is there a command to compact the ending parens?

  Xah
∑ http://xahlee.org/

☄