2698 2006-01-11 18:50:31 +0000 [XSLT] what if $group-number is a negative integer 2006-02-02 19:38:12 +0000 1 1 1 Unclassified XPath / XQuery / XSLT XSLT 2.0 Candidate Recommendation All All CLOSED FIXED P2 normal --- 1 joannet mike public-qt-comments oldest_to_newest 7782 0 joannet 2006-01-11 18:50:31 +0000 The second paragraph in section 15.2 reads: "The Nth captured substring (where N > 0) is the string matched by the subexpression contained by the Nth left parenthesis in the regex. The zeroeth captured substring is the string that matches the entire regex. This means that the value of regex-group(0) is initially the same as the value of . (dot)." Is N < 0 an error? 7793 1 mike 2006-01-11 20:02:25 +0000 The next sentence after your extract answers the question: The function returns the zero-length string if there is no captured substring with the relevant number. 8113 2 mike 2006-02-02 19:37:35 +0000 I have added another item to the list of conditions under which a zero-length string is returned: * The number is negative.