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From: Stefan Monnier <monnier@iro.umontreal.ca>
Newsgroups: gmane.emacs.help
Subject: Re: How to check whether the current line is a comment-only one?
Date: Thu, 18 Aug 2016 03:44:31 -0400
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> is there a predicate function to determine whether the line the point is
> in is entirely a comment line?

I don't think there is one yet.  Depending on what you mean by "entirely
a comment", it could be:

    (save-excursion
      (forward-line 0)
      (< (line-end-position)
         (let ((ppss (syntax-ppss)))
           (when (nth 4 ppss)
             (goto-char (nth 8 ppss)))
           (forward-comment (point-max))
           (point))))


-- Stefan