Hi John, It was my mistake. Thank you for clarification! -------------- Yutaka Emura Emurasoft, Inc. http://www.emurasoft.com/ E-mail: yutaka@emurasoft.com -----Original Message----- From: John Maddock [mailto:john_maddock@compuserve.com] Sent: Wednesday, January 01, 2003 3:47 AM To: Boost-Users@yahoogroups.com Subject: Re: [Boost-Users] RegEx: (?= ) and (?! )
I am using RegEx in Boost v1.29.0. (?= ) and (?! ) expressions do not seem to work at a certain condition.
In the following example, "(?=a)b" should match "b" in "xyzabcdefg", but does not.
Which is correct: (?=a) is a forward lookahead *possitive* assertion, so (?=a)b can never match anything since the next character can't be both an 'a' and a 'b' at the same time!
Similarly, "(?!a)b" should not match "b" in "xyzabcdefg" but it does.
It should match: (?!a) will match anything except 'a' so (?!a)b will match the next 'b' that it finds. John Maddock http://ourworld.compuserve.com/homepages/john_maddock/index.htm Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/