Matching regular expressions in c++

Hi all

I have the following problem. I am using PERL language to read text file, and in this file I use pattern matching to search for specific line formatting. I need this because I am analyzing big code output.
For instance if I look for line such as
44.333e-02 44.221e-03 22.332e-04

I can define in PERL

Code:

---

if($line=~/(\d{2}\.\d{3}e-\d{2}) +(\d{2}\.\d{3}e-\d{2}) +(\d{2}\.\d{3}e\d{2})/)
{
$a[$i++]=$1 ;

$B[$j++]=$2 ;

$C[$k++]=$3 ;

}

---

Where $1,$2,$3 are perl notation to say what is matched in the first second third bracket . This shall store the desired objects matched in the above specified pattern in @A,@B,@C arrays.
Is it possible to do this in C++. In ordinary C there are functions regcomp() regexec() which are an option but are rather complicated compared with the simple perl procedure.

Thank you in advance

Like this perhaps?
Boost.Regex

This is ok, but can't I manage my goal with standard package libraries. Because after all I would like to do it as simple as possible.

Sure you can, but rewriting regex from scratch won't be that easy, unless you're willing to compromise on a lot of features.

Or you could take a less literal translation of Perl to C++, and instead write a custom validation routine for a string with two characters, followed by dot, followed by...

What exactly are you hoping to get by doing this in C++, which you can't do in Perl?

Quote:

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Originally Posted by wronski11

This is ok, but can't I manage my goal with standard package libraries.

---

There is no regex support in the C++ standard library at the moment, hence you would have to implement it yourself. That said, you may be able to use std::tr1::regex (i.e., regex support from the TR1 extensions to the standard library), or even std::regex (as an "early adopter": it is pretty much the same as std::tr1::regex anyway, which was adapted from Boost.Regex).

Well first of all thank you for the very professional opinion. I installed the boost.regex library but got problems compiling c++ code which uses it. I used the following command to compile my code

Code:

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g++ -o ZZ test.cpp –I/home/boost/boost_1_45_0/libs/regex/build/gcc/boost_regex-gcc-1_45/ -L/home/boost/boost_1_45_0/libs/regex/build/gcc/libboost_regex-gcc-1_45.a

---

In short I am giving the paths to de library and the includes . However it does not run. The actual code i compile is : (code downloaded form the internet)

Code:

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

using namespace std;

int main( ) {

  std::string s, sre;
  boost::regex re;

  while(true)
  {
      cout << "Expression: ";
      cin >> sre;
      if (sre == "quit")
      {
        break;
      }
      cout << "String:    ";
      cin >> s;

      try
      {
        // Set up the regular expression for case-insensitivity
        re.assign(sre, boost::regex_constants::icase);
      }
      catch (boost::regex_error& e)
      {
        cout << sre << " is not a valid regular expression: \""
              << e.what() << "\"" << endl;
        continue;
      }
      if (boost::regex_match(s, re))
      {
        cout << re << " matches " << s << endl;
      }
  }
}

---

Does anyone knows why this does not work?


The actual error reads as follows

Code:

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ccYuUtqf.o: In function `boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::assign(char const*, char const*, unsigned int)':
test.cpp:(.text._ZN5boost11basic_regexIcNS_12regex_traitsIcNS_16cpp_regex_traitsIcEEEEE6assignEPKcS7_j[boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits'
/home/tmp/ccYuUtqf.o: In function `boost::re_detail::perl_matcher<__gnu_cxx::__normal_iterator<char const*, std::basic_string<char, std::char_traits<char>, std::allocator:
test.cpp:(.text._ZN5boost9re_detail12perl_matcherIN9__gnu_cxx17__normal_iteratorIPKcSsEESaINS_9sub_matchIS6_EEENS_12regex_traitsIcNS_16cpp_regex_traitsIcEEEEEC1ES6_S6_RNS_13matc'
/home/tmp/ccYuUtqf.o:(.gcc_except_table+0xa4): undefined reference to `typeinfo for boost::regex_error'
/home/tmp/ccYuUtqf.o: In function `bool boost::regex_match<__gnu_cxx::__normal_iterator<char const*, std::basic_string<char, std::char_traits<char>, std::allocator<char> :
test.cpp:(.text._ZN5boost11regex_matchIN9__gnu_cxx17__normal_iteratorIPKcSsEESaINS_9sub_matchIS5_EEEcNS_12regex_traitsIcNS_16cpp_regex_traitsIcEEEEEEbT_SD_RNS_13match_resultsISD'
collect2: ld returned 1 exit status

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