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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=9556 Subgroup wrong when matching (.)(?=(.)) against "XY"? [EMAIL PROTECTED] changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED ------- Additional Comments From [EMAIL PROTECTED] 2002-06-01 00:39 ------- Perl does fill $2 with Y. And so does Perl5Matcher. If you look at the group offsets, you'll find the matching is performed correctly. In other words, two groups are found and the begin and end offsets of the second group are 1 and 2. However, because the matched group was a zero-width lookahead assertion, the Y character is not consumed and not considered part of the full match. So the full match is just 'X'. Since the full match stored in the MatchResult is 'X', offsets that exceed the length of the match result in empty strings. To show that the full match is just 'X' in Perl, look at group 0 here: ~> perl -e '"xy" =~ /(.)(?=(.))/; print "0: $& 1: $1 2: $2 3: $3\n";' 0: x 1: x 2: y 3: Now, the problem we're faced with is one that I'm not sure how to deal with. Is the capturing of the lookahead assertion an undefined side-effect, much as some situations involving the capturing of repetitions used to be before Perl 5.6? Or is it intended for a groups that match outside of the full match to be saved? It's actually quite tricky to implement this without either maintaining a reference to a copy of the entire original input (undesirable) or screwing up a lot of other cases. I'd like to mull this one over for a while. In the meantime, the workaround is to use the group offset information to extract the appropriate substring from the input. -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
