regular expression Can't find sequence of numbers - c++

Question

Let
exp = ^[0-9!##$%^&*()_+-=[]{};':"\|,.<>/?\s]*$
be a regular expression that allows me to find all sequences of numbers with or without special characters.
by using exp I manage to extract all sequences of numbers that are greater than 5. But the number 98200 cannot be extracted. I am not using any limits to how long should the sequence of numbers be.
Source code:
#include <boost/regex.hpp>
#include iostream;
using namespace std;
int main()
{
string s = "16000";
string exp = ^[0-9!##$%^&*()_+-=[]{};':"\\|,.<>\\/?\\s]*$
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;
}

Answer 1

In C#, you need to escape the ]. You don't need to escape [ {} () when they are inside a character class. Also, if you want to include the dash as an included character in the character class, it should be at the beginning or end of the list. The sequence that you have of +-= translates to [+,-./0123456789:;<=] which makes your regex redundant. Finally, because of the terminal quantifier, you are allowing matching of zero length strings. This may be what you want, but if not, consider the '+' quantifier.
What about simply
[^A-Za-z]+
with or without the ^ $ anchors at the beginning/end

Answer 2

Indiscriminately escaping everything works for me.. :)
string exp = "^[0-9\\!##\\$\\%\\^&*\\(\\)_\\+\\-=\\[\\]\\{\\};\\\':\\\"\\\\|,\\.<>\\/?\\s]*$";
Note the double backslash... I'm sure you can workout which of the characters in your list means anything special, and only escape those, as I don't have the time to lookup what has special meaning in this context, I escaped everything, and this works fine for a few of the cases I tested
16000 => returns 1 16A000 => returns 0 16#000 => returns 1
Which I'm guessing is what you want...

Answer 3

I have shifted the brackets to the front of the character class and therewith I get the output 1 for 98200 using the following code:
#include <string>
#include <boost/regex.hpp>
#include <iostream>
using namespace std;
int main()
{
std::cout << "main()\n";
string s = "98200";
string exp = "^[][0-9!##$%^&*()_+-={};':\"\\|,.<>\\/?\\s]*$";
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:
*/
EDIT: Note, that I used my experience with emacs regular
expressions. The info pages of emacs explain: "To include a ] in a
character set, you must make it the first character." I tried this
with boost::regexp and it worked. Later on when I had more time I read
in the boost manual
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
that this is not specified for the perl regular expression syntax.
The perl syntax is the standard setting for boost::regex. According to the
specification the comment by
https://stackoverflow.com/users/2872922/ron-rosenfeld is the best
answer.
In the following program I eliminate the character range which was incidentally encoded into your regular expression.
Testing shows that the bracket at the beginning of the character set is included into the character set. So it turns out that my statement was right even if it is not specified in the official manual of boost::regex.
Nevertheless, I suggest that https://stackoverflow.com/users/2872922/ron-rosenfeld inserts his comment as an answer and you mark it as the solution. This will help others reading this thread.
#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!##$%^&*()_+={};':\"|,.<>/?\\s-]*$";
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:
*/
I asked at http://lists.boost.org/boost-users/2013/12/80707.php
The answer of John Maddock (the author of the boost::regex library) is:
>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?
It's a feature, both Perl and POSIX extended regular expression behave the
same way.
John.