Re: [Boost-users] [regex] Perl regex special characters

From: Andriy Tylychko \(mail.ru\) (telya_at_[hidden])
Date: 2006-09-08 14:01:53

> From: Roman Neuhauser [mailto:neuhauser_at_[hidden]] 
> # telya_at_[hidden] / 2006-09-08 12:23:36 +0300:
> > Hi
> >  
> >  <http://www.boost.org/libs/regex/doc/syntax_perl.html>
> > http://www.boost.org/libs/regex/doc/syntax_perl.html says:
> > 
> > 
> > Perl Regular Expression Syntax
> > 
> > 
> > In Perl regular expressions, all characters match themselves except 
> > for the following special characters:
> > 
> > .[{()\*+?|^$
> 
> > Q: what about "]}" symbols?
> 
>     They're only special if there's a matching "[" or "{" 
> earlier in the
>     pattern: 
> 
>     > echo 'aaa]}]}]}bbb' | perl -pe 's/(]|})+//'
>     aaabbb
>     > echo 'aaa]}]}]}bbb' | perl -pe 's/[]}]+//'
>     aaabbb
>     > echo 'aaa}}}]]]bbb' | perl -pe 's/}+//;s/]+//'
>     aaabbb
> 

Moving this discussion from boost-users to boost-development...

Thanks for explanation, Roman. 

I've checked this on boost v.1.33.1, but only unmatched "]" is allowed,
construction of boost::regex("}") claims unmatched "}". Is it by design or
already fixed in v.1.34?

I had to handle special characters, so I just "copy/paste"ed from docs. And
so, I didn't handle "}]". Do you think it's a good idea to expand
description of special characters in docs to include explanation about "}]"
characters? 
As I checked, both unmatched "]" (and probably "}" in 1.34) and unmatched
but escaped "\}\]" are allowed and have the same effect. It was very useful
for me, so maybe it's worth to mention in docs too.

Thanks,
Andriy.