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Re: c-mode syntax strings and regexp word boundaries

From: Andreas Röhler
Subject: Re: c-mode syntax strings and regexp word boundaries
Date: Wed, 11 Sep 2013 10:57:05 +0200
User-agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130801 Thunderbird/17.0.8

Am 06.09.2013 22:19, schrieb Alan Mackenzie:
Hi, Jon.

On Thu, Sep 05, 2013 at 10:14:16PM -0700, Jon Dufresne wrote:

I am trying to modify a major mode derived from c-mode. I am adding support
for an alternative string syntax (PHP heredoc). To do this I am using
"syntax-propertize-function" and
"syntax-propertize-extend-region-functions". (As an aside I am not sure
this is the best approach, but it is best I have come up with so far.)

When trying to extend the propertize region, a regexp fails, but I am not
clear as to why. I have isolated the problem with the following test case.

   (insert "END;\n")
   (goto-char (point-min))
   (message "Search forward first time")
   (re-search-forward "^END\\b")
   (put-text-property (1- (point)) (point)
                      'syntax-table (string-to-syntax "|"))
   (goto-char (point-min))
   (message "Search forward second time")
   (re-search-forward "^END\\b"))

Thanks for any help.

Not what you asked, but as a suggestion, you might want to use the CC
Mode macros which deal with text properties on single characters.  For
example, you could have used `c-put-char-property' instead of

This has the following pros/cons: (i) these macros are slightly less
cumbersome to use, since they take only a single position parameter; (ii)
They also work in XEmacs; (iii) there is some effort involved in learning
about them and how they work.

If you're interested, search cc-defs.el for

     Macros/functions to handle so-called "char properties",

and read the definitions in that page.

Just for the record:

the error in the present case was the wrong position, which would fail also 
with a single char.

Instead of

 (put-text-property (1- (point)) (point)

 (put-text-property (point) (1+ point))

should work


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