[Boost-users] boost::regex Character set including braces

Subject: [Boost-users] boost::regex Character set including braces
From: Tobias (i_at_[hidden])
Date: 2013-12-04 04:27:48

Dear boost-users,
in the post

http://stackoverflow.com/questions/20351369/regular-expression-cant-find-seq
uence-of-numbers

I discovered that if one uses an closing bracket as the first character of a
character class the character class includes this bracket.
This works with the standard setting of boost::regex (i.e., perl-regular
expressions) but it is not documented in the
manual page

http://www.boost.org/doc/libs/1_55_0/libs/regex/doc/html/boost_regex/syntax/
perl_syntax.html#boost_regex.syntax.perl_syntax.character_sets

Is this an undocumented feature, a bug or did I misinterpret something in
the manual?
The version information in version.hpp is:

#define BOOST_LIB_VERSION "1_53"

Info: I tried this specification of the bracket in the character set because
I am used to it from emacs regular expressions.
In the remainder there follows a program for reproduction of the phenomenon:

#include <string>
#include <boost/regex.hpp>
#include <iostream>

using namespace std;

int main()
{
    std::cout << "main()\n";
    string s = "98[2]00";
    string exp = "^[][0-9]*$";
    const boost::regex e(exp);
    bool isSequence = boost::regex_match(s,e);
    //isSequence is boolean and should be equal to 1 
    cout << isSequence << endl;

  return 0;
}

/**
     Local Variables:
     compile-command: "g++ -g test.cc -o test.exe -lboost_regex-mt;
./test.exe"
     End:
*/

 

Best regards / Mit freundlichen Grüßen

Tobias Zawada
Engineering / Software Development

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