[Boost-users] Regex problem: cannot parse terms containing OR

Subject: [Boost-users] Regex problem: cannot parse terms containing OR
From: Ramon F Herrera (ramon_at_[hidden])
Date: 2009-09-26 19:04:04

I have been able to parse stuff more complicated than this, but now I am 
stuck with something seemingly simpler.

The expression being parsed is the common sequence:

   1,2-5,7,8-11

Question 1: Notice my approach. I first match the whole expression, with 
"regex_match", to make sure that it is valid (that works great). Next, I 
use "regex_iterator" to break down the parts. Is that good practice? Am 
I being inefficient/redundant?

Question 2: My code below only extracts "range terms" ("x-y"), for some 
reason I cannot extract "number terms".

As a workaround, I can always feed my data like this:

1-1,2-5,7-7,8-11

but, after a lot of tries, would love to learn how to do this properly.

TIA,

-Ramon

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

#include <iostream>
#include <boost/regex.hpp>
using namespace std;

bool
term_callback(const boost::match_results<std::string::const_iterator>& what)
{
     for (unsigned int i = 0; i < what.size(); i++) {
         cout << "what[" << i << "]: " <<  what[i].str() << endl;
         cout << "---------" << endl;
     }
     return true;
}

int
main(int argc, char *argv[])
{
     const char hyphen      = '-';
     const char left_paren  = '(';
     const char right_paren = ')';
     const char bar         = '|';
     const char comma       = ',';
     const char star        = '*';

     const string number    = "[0-9]+";
     const string range     = number + hyphen + number;
     const string term      = left_paren + number + bar + range + 
right_paren;
     const string sequence  = term + bar + left_paren + term + comma + 
right_paren + star + term;

     boost::regex expression(sequence);
     boost::regex piece(range);
     boost::cmatch matches;

     char argument[1024];
     strcpy(argument, argv[1]);

     if (!boost::regex_match(argument, matches, expression)) {
         cerr << "There is no match" << endl;
         return 1;
     }

     string text = argument;

     boost::sregex_iterator m1(text.begin(), text.end(), piece);
     boost::sregex_iterator m2;
     for_each(m1, m2, &term_callback);

     return 0;
}