Re: [Boost-users] question on boost::regex expression(query);

From: Mike Marchywka (marchywka_at_[hidden])
Date: 2007-10-02 08:28:26

>Variable length look-behind isn't support by Boost.Regex (or by Perl for
>that matter).
>
>Sorry I can't be more helpful at present: although it seems as though
>lookbehind isn't really needed in this case - you could remove the
>lookbehind and use a marked sub-expression to identify the section you want
>instead.

The subexpression was the whole point of trying boost so I will assume you
are right and continue. However, the inability to catch the problem with 
(...) combined with
the linker comment made me a little concerned about the build accuracy.

Thanks.

>From: "John Maddock" <john_at_[hidden]>
>Reply-To: boost-users_at_[hidden]
>To: <boost-users_at_[hidden]>
>Subject: Re: [Boost-users] question on boost::regex expression(query);
>Date: Tue, 2 Oct 2007 10:09:56 +0100
>
>Mike Marchywka wrote:
> >> Hi,
> >> I'm new to boost and not all that familiar with Perl regex. However,
> >> I have my own
> >> code for using Perl regex libraries for finding interesting features
> >> in DNA (
> >> 
>http://www.mail-archive.com/[e-mail]/msg01382.html
> >> )
> >>
> >> I recently added boost to work along with Microsoft's greta code.
> >> However, I now
> >> have a problem with regex exploding.
> >> The questionable regex is presumably,
> >>
> >> (?<=GU.*?TACTAAC.{20,40}AG|^).*?(?=GU.*?TACTAAC.{20,40}AG|$)
>
>Variable length look-behind isn't support by Boost.Regex (or by Perl for
>that matter).
>
>Sorry I can't be more helpful at present: although it seems as though
>lookbehind isn't really needed in this case - you could remove the
>lookbehind and use a marked sub-expression to identify the section you want
>instead.
>
>So I think (?GU.*?TACTAAC.{20,40}AG|^)(.*?(?=GU.*?TACTAAC.{20,40}AG|$))
>would be equivalent, with $1 containing the section you're interested in?
>
>HTH John.
>
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>Boost-users_at_[hidden]
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