Re: [Boost-bugs] [Boost C++ Libraries] #2165: regex_search match but regex_match is not filled

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #2165: regex_search match but regex_match is not filled
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2008-08-05 10:56:48

#2165: regex_search match but regex_match is not filled
-----------------------------------+----------------------------------------
  Reporter:  mickael_at_[hidden]  |       Owner:  johnmaddock             
      Type:  Bugs                  |      Status:  closed                  
 Milestone:  Boost 1.36.0          |   Component:  regex                   
   Version:  Boost 1.35.0          |    Severity:  Problem                 
Resolution:  invalid               |    Keywords:  regex_search regex_match
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Changes (by johnmaddock):

  * status:  new => closed
  * resolution:  => invalid

Comment:

 I believe this is a misunderstanding of how regular expressions work: if
 the expression is [a-z]* then it is perfectly legal to match a zero-length
 string if the * operator ''repeats zero times''.  So for example [a-z]*
 matched against the string " abc " can find 4 matches:

 * the zero length string at the start of the " abc ".
 * the string "abc".
 * the zero length string after the "c".
 * the zero length string at the end of " abc ".

 When a zero length string is matched, then sub_match::first ==
 sub_match::second and sub_matched::matched == true.

 Probably you meant to use [a-z]+ as the regular expression?

 If this doesn't clarify the issue, or if I've misunderstood, please reopen
 the ticket.

 HTH & bonjour, John Maddock.

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/2165#comment:1>
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