Re: [Boost-bugs] [Boost C++ Libraries] #8304: Regex not matching case in character ranges if collate flag specified

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #8304: Regex not matching case in character ranges if collate flag specified
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-03-21 18:46:04

#8304: Regex not matching case in character ranges if collate flag specified
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  Reporter:  dave@…               |       Owner:  johnmaddock
      Type:  Bugs                 |      Status:  closed     
 Milestone:  To Be Determined     |   Component:  regex      
   Version:  Boost 1.51.0         |    Severity:  Problem    
Resolution:  invalid              |    Keywords:             
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Comment (by johnmaddock):

 > Isn't case insensitive collation different from case sensitive
 collation?

 Yes, since this is wide characters on Win32, it's basically Unicode
 collation: http://www.unicode.org/reports/tr10/#Multi_Level_Comparison

 which is based on "levels".

 So character shape first, then accent, then case, then some other
 differences.  That means that 'a', 'Ã ' and 'A' collate next to each other
 followed by 'b' and 'B' if case sensitivity is on, while if matching is
 case insensitive then 'a' and 'A' are treated as equivalent (ie collate
 the same), but 'Ã ' is still separate.

 >Your comment seems to suggest that collation is an odd or unusual thing.
 We use the regex engine to allow users to search through text and they
 expect to be able to use '[a-z]+' and match against 'Années'. I guess we
 could add a 'Foreign language support' option to support both cases, I
 just wanted to make sure that the Boost implementation was 'correct'.

 Sigh... I see where you're coming from, (and why your users would want
 that), but regex would have to implement it's own collation algorithm to
 support that.  You could probably do that yourself actually by using a
 custom traits class?

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8304#comment:4>
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