Re: back references in regexen

Hi Ashok, hi F'n'O taskforce

 > Thank you for your note dated May 21, 2003 re. back references in
 > Regular expressions:
 > http://lists.w3.org/Archives/Public/public-qt-comments/2003May/0288.html
 >
 > The Functions and Operators taskforce discussed your request during
 > its  telcon on June 12, 2003.

Thanks for considering my request.

 > While the functionality you suggest is interesting, it is complex

As I have shown on the list, it's easy to learn and use, extremely 
common in most if not all popular programming languages [2][3], and 
available in popular regex libraries [2], which results in a lower cost 
of implementation. Many developers (meaning "users" not implementers) 
are familiar with back references in regexen, and will miss them.

 > and
 > the taskforce felt that the additional complexity

The feature is not really complex. Try to match an XML attribute (which 
can have two different deleimiters), and you are happy to have backrefs.

 > was not warranted at this point.

I did show you a use case [1]:

I am marking up XML code listings with XHTML markup using XSLT 2; syntax 
markup for syntax highlighting. The requested functionality in this case 
would

   * save lots of redundant code, and
   * enable me to express my intent very clearly, thus
   * make the code much more readable and maintainable.

 > Also, we are trying to stay close the regular expression
 > facilities in XML Schema which do not have this functionality.

IMHO they should have it too, and I hope they will add it in the future. 
Since the regexen in your spec are based on the WXS spec: Perhaps you 
could forward my request? (eg URLs of the posts)

F'n'O should have the feature in the next recommendation, even if WXS 
currently doesn't have it before that.

 > Please let us know if you are satisfied with this response.

I believe that back references are a feature that should be available to 
developers working with XSLT, XPath, XQuery, and similiar languages. 
It's a very basic, very general, and very useful feature, which has been 
widely available to developers and even users (sed on the comandline 
[3]) since the long gone days of Bell Labs Unix.

Tobi

[1]
http://lists.w3.org/Archives/Public/public-qt-comments/2003May/0288.html
[2]
http://lists.w3.org/Archives/Public/public-qt-comments/2003May/0298.html
[3]
http://lists.w3.org/Archives/Public/public-qt-comments/2003May/0307.html

-- 
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Received on Friday, 13 June 2003 10:21:53 UTC