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Re: Back references inside character classes

From: Michael Kay <mike@saxonica.com>
Date: Sun, 02 Jan 2011 19:56:33 +0000
Message-ID: <4D20D871.2030900@saxonica.com>
To: "Paul J. Lucas" <paul@lucasmail.org>
CC: public-qt-comments@w3.org
On 02/01/2011 17:01, Paul J. Lucas wrote:
> The W3C test K2-MatchesFunc-11:
>
> 	matches("abcd", "(asd)[\1]")
>
> tests that an XQuery implementation should raise the FORX0002 error for a back reference inside a character class.  However, after reading:
>
> * XQuery and XPath Functions and Operators, section 7.6.1
> * XML Schema Part 2, appendix F
>
> I can't find where any specification explicitly forbids it.  Can somebody point me to the section of a specification that does?  Thanks.
>
It's stated twice in section 7.6.1 
(http://www.w3.org/TR/xpath-functions/#regex-syntax):

(a) "Back-references are allowed outside a character class expression."

(b) Note: Within a character class expression, \ followed by a digit is 
invalid. Some other regular expression languages interpret this as an 
octal character reference.

Michael Kay
Saxonica
Received on Sunday, 2 January 2011 19:57:03 UTC

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