Re: Printing comment-start of various modes

[Stephen Berman <stephen.berman@gmx.net>]

On Tue, 13 Aug 2024 20:09:57 +0000 Heime <heimeborgia@protonmail.com> wrote:

> This function should print the value of comment-start for various modes,
> but I am not getting any comment-start outputs from it.
>
> (defun costart ()
>   "Loop through various major modes and print the value of `comment-start`."
>
>   (interactive)
>
>   (let ( (modes '(sh-mode perl-mode python-mode
> 		 emacs-lisp-mode lisp-interaction-mode
>                  org-mode tex-mode latex-mode texi-mode
>                  c-mode c++-mode f90-mode fortran-mode
>                  html-mode css-mode js-mode
>                  java-mode php-mode) )
>
>          (output-buffer (generate-new-buffer "Costart")) )
>
>     (with-current-buffer output-buffer
>       (insert "Mode \t\t Comment Start \n")
>       (insert "---- \t\t ------------- \n"))
>
>     (dolist (mode modes)
>       (with-temp-buffer
>         (funcall mode)
>         (let ((comment-start (or comment-start "None")))
>           (with-current-buffer output-buffer
>             (insert (format "%s \t\t %s \n" mode comment-start))))))
>
>     (switch-to-buffer output-buffer)))

You successively bind mode-specific value of comment-start in a
temporary buffer, and then switch to output-buffer to print the values,
but this buffer is in fundamental-mode, where comment-start has the
value nil by default.  Using the temporary buffer seems superfluous, you
could just use output-buffer:

(defun costart ()
  "Loop through various major modes and print the value of `comment-start`."
  (interactive)
  (let ((modes '(sh-mode perl-mode python-mode
			 emacs-lisp-mode lisp-interaction-mode
			 org-mode tex-mode latex-mode texi-mode
			 c-mode c++-mode f90-mode fortran-mode
			 html-mode css-mode js-mode
			 java-mode php-mode) )
        (output-buffer (generate-new-buffer "Costart")))
    (with-current-buffer output-buffer
      (insert "Mode \t\t Comment Start \n")
      (insert "---- \t\t ------------- \n"))
    (dolist (mode modes)
      (with-current-buffer output-buffer
        (funcall mode)
        (let ((comment-start (or comment-start "None")))
          (insert (format "%s \t\t %s \n" mode comment-start)))))
    (switch-to-buffer output-buffer)
    (fundamental-mode)))

Steve Berman