[Boost-bugs] [Boost C++ Libraries] #13156: Not word boundary - \b vs. NOT \B are not the same

Subject: [Boost-bugs] [Boost C++ Libraries] #13156: Not word boundary - \b vs. NOT \B are not the same
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-08-10 01:36:31

#13156: Not word boundary -  \b   vs. NOT \B are not the same
----------------------------------+--------------------------
 Reporter:  anonymous             |      Owner:  John Maddock
     Type:  Bugs                  |     Status:  new
Milestone:  To Be Determined      |  Component:  regex
  Version:  Boost 1.64.0          |   Severity:  Showstopper
 Keywords:  Not Word Boundary \B  |
----------------------------------+--------------------------
 I am reposting this from another source.

 In theory, \B should match everywhere \b doesn't.

 In boost regex, this is not the case at the beginning nor end of string.

 Below is a list of test results from a few Perl-like engines.
 Apparently, this was fixed in Perl v5.22 (below shows v5.20).
 The only engines that seem to handle this correctly is PHP and
 ECMAScript.

 ------------------------------------------------

 {{{

 Target      = '   ssssssssssssss '
 Replacement = '<>'

 ==================================================
 PHP 7.03

 \b      = '   <>ssssssssssssss<> '
 \B      = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?!\b)  = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?<!\b) = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?!\B)  = '   <>ssssssssssssss<> '
 (?<!\B) = '   <>ssssssssssssss<> '

 =======================================
 Perl 5.20

 \b      = '   <>ssssssssssssss<> '
 \B      = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s '
 (?!\b)  = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?<!\b) = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?!\B)  = '   <>ssssssssssssss<> '
 (?<!\B) = '   <>ssssssssssssss<> '

 ========================================
 Boost 1.64

 \b      = '   <>ssssssssssssss<> '
 \B      = ' <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s '
 (?!\b)  = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?<!\b) = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?!\B)  = '<>   <>ssssssssssssss<> <>'
 (?<!\B) = '<>   <>ssssssssssssss<> <>'

 =====================================
 JavaScript

 \b      = '   <>ssssssssssssss<> '
 \B      = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?!\b)  = '<> <> <> s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s<>s <>'
 (?!\B)  = '   <>ssssssssssssss<> '

 }}}

-- 
Ticket URL: <https://svn.boost.org/trac10/boost/ticket/13156>
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