Re: [Boost-users] Regex: Invalid preceding regular expression problem

From: John Maddock (john_at_[hidden])
Date: 2007-10-31 05:58:34

Brian Krahmer wrote:
> Hello,
>  I'm a new member to the mailing list.  BTW, thanks to everyone who
> contributes to boost.  It's a fantastic software.  I am having a
> problem with building an expression object.  The line in question
> reads 'boost::regex expression(pattern, options);', where I'm using
> the boost::regex::extended option, and the pattern looks like this:
> "^([0-7]\\..*|8\\.0(\\.[0-3](\\.[0-3])?)?)[^.0-9]*?$".  I fired up a
> ruby interpreter, and it handled the regex fine (using "8.0.0.1
> (en-US)" as a positive, and "9.0.0.1 (en-US)" as a negative).  Can
> anybody tell me what is wrong with this regex, or confirm that there
> may be a bug in the library?

Nope there's a bug in the options you are using - boost::regex::extended 
enables the "POSIX extended" flavour of regular expressions - and these 
don't support non-greedy repeats.  Use boost::regex::perl if you want to use 
these (since you are using Perl-style regexes).

HTH, John.