Re: How do you check if the current point is in a comment or a string? (Was Re: Problems with syntax-ppss: Was [... Apply `comment-depth' text properties when calling `back_comment'.])

[Andreas Röhler]

On 10.03.2016 15:28, Stefan Monnier wrote:
> > > (nth 8 (syntax-ppss)) works fine for me in something like ";; some
> > > comment in an emacs-lisp-mode buffer"; it returns the starting point
> > > of the comment.
> > Does it really? For me it returns nil when the point is as shown below:
> >    <point>;; some comment in an emacs-lisp-mode buffer
> That's correct, because point is *not* inside the comment.
>
> > In all these cases, the font trick works.
> Here it's because `get-text-property' returns the property of the
> character after point, and indeed this is ";" which is in the comment.
>
> IOW they're both correct because they don't ask the same thing.
>
> > In C mode, it returns nil in the following two positions:
> >
> >    /<point>/ asd
> >    <point>// asd
> >
> > As well as these two:
> >
> >    <point>/* asd */
> >    /<point>* asd */
> Indeed, this is a current problem with parse-partial-sexp (and hence
> syntax-ppss) and is directly related to what Alan was referring to.

Can't see any issue with parse-partial-sexp - see attachment.

> Given the way parse-partial-sexp works (i.e. it can only look at the
> text that precedes), even if we fix it, parse-partial-sexp wouldn't be
> able to tell you that <point> is inside a comment.

That's dead wrong: parse-partial-sexp may scan  from BOB - and it must 
in certain cases to detect being in comment or not. If it must scan from 
BOB or not depends from language resp. syntax of comments.

>    But it could tell
> you that it's in the middle of something that could turn out to be
> a comment.
>
>
>          Stefan

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