Comment syntax

Comment syntax

[Alex Branham]

Hello -

I am trying to write Emacs support for a major mode where * (an
asterisk) starts a comment, but only if * is at the beginning of the
line (comments started this way end at the end of the line). I've read
through (info "(elisp) Syntax Flags") about how to support this but
nothing there seems to help (unless I missed something, which is very
possible.) Is there a way to get bol-* recognized as starting a comment?

Any pointers appreciated,
Alex

Re: Comment syntax

[Stefan Monnier]

> I am trying to write Emacs support for a major mode where * (an
> asterisk) starts a comment, but only if * is at the beginning of the
> line (comments started this way end at the end of the line). I've read
> through (info "(elisp) Syntax Flags") about how to support this but
> nothing there seems to help (unless I missed something, which is very
> possible.) Is there a way to get bol-* recognized as starting a comment?

You need to setup a syntax-propertize-function for that.

E.g.

    (setq-local syntax-propertize-function
        (syntax-propertize-rules ("^\\*" (0 "<"))))


        Stefan

Re: Comment syntax

[Alex Branham]

On Fri 28 Jun 2019 at 08:37, Stefan Monnier <monnier@iro.umontreal.ca> wrote:

>> I am trying to write Emacs support for a major mode where * (an
>> asterisk) starts a comment, but only if * is at the beginning of the
>> line (comments started this way end at the end of the line). I've read
>> through (info "(elisp) Syntax Flags") about how to support this but
>> nothing there seems to help (unless I missed something, which is very
>> possible.) Is there a way to get bol-* recognized as starting a comment?
>
> You need to setup a syntax-propertize-function for that.
>
>     (setq-local syntax-propertize-function
>         (syntax-propertize-rules ("^\\*" (0 "<"))))

Thanks, I didn't know about syntax-propertize-rules. This seems make
everything after the asterisk a comment, though, so with this buffer:

* this is a comment

but so is this :-(




I thought that modifying it to:

  (setq-local syntax-propertize-function
              (syntax-propertize-rules ("^\\*.*$" (0 "<"))))
              
might work, but that doesn't seem to do the trick either. 

Alex