Question

Edit8: I’ve posted the solution first for anyone who might come along after me with the same problem.

Solution:

Assigned regex with = instead of invoking the () operator. Worked fine. That was stupid.

#include <iostream>
#include <string>
#include <boost/xpressive/xpressive_dynamic.hpp>

int main()
{
    std::string str = "foobarfoo";
    boost::xpressive::sregex rex;
    std::string rstr = "foo";
    rex = boost::xpressive::sregex::compile(rstr, boost::xpressive::regex_constants::ECMAScript);
    if (boost::xpressive::regex_search(str, rex, boost::xpressive::regex_constants::match_continuous))
        std::cout << "Match found.";
    else
        std::cout << "No match found.";
    return 0;
}

Original Problem:

I’ve been fighting with xpressive for a while now, and I’ve yet to make anything work. With the following code:

#include <iostream>
#include <string>
#include <boost/xpressive/xpressive_dynamic.hpp>

int main()
{
    std::string str = "foobar";
    boost::xpressive::sregex rex;
    std::string rstr = "foo";
    rex(boost::xpressive::sregex::compile(rstr));
    if (boost::xpressive::regex_match(str, rex))
        std::cout << "Match found.";
    else
        std::cout << "No match found.";
    return 0;
}

I’m not finding the match I expect. Help would be greatly appreciated.

Edit: Tried changing the regex compile line to

rex(boost::xpressive::sregex::compile(rstr, boost::xpressive::regex_constants::ECMAScript));

Still nothing.

Edit2: Compiling with MinGW GCC 4.7

Edit3: I also tried changing the line where the regex string is declared to both

std::string rstr = ".*";

and

std::string rstr = "(.*)";

Still nothing.

Edit4: I’ve not got the following, still with no results:

#include <iostream>
#include <string>
#include <boost/xpressive/xpressive_dynamic.hpp>

    int main()
    {
        std::string str = "foobarfoo";
        boost::xpressive::sregex rex;
        std::string rstr = "(foo)";
        rex(boost::xpressive::sregex::compile(rstr));//;, boost::xpressive::regex_constants::ECMAScript));
        if (boost::xpressive::regex_search(str, rex, boost::xpressive::regex_constants::match_default))
            std::cout << "Match found.";
        else
            std::cout << "No match found.";
        return 0;
    }

Edit5: I’m expecting two matches at this point, the “foo” at both the beginning and end of str.

Edit6: Tried running regex_search with the match_continuous flag set hoping I could at least get it to pick up the prefix. No dice. Also tried compiling with ECMAScript flag and running regex_search with both match_default and match_continuous flags.

Edit7: I know strstr() will work here. That’s because this is a simple sample case. Boost is imperative in the actual application.

Answer 1

#include <iostream>
#include <string>
#include <boost/xpressive/xpressive_dynamic.hpp>

int main()
{
    std::string str = "foobar";
    std::string rstr = "foo";
    boost::xpressive::sregex rex = boost::xpressive::sregex::compile(rstr);
    if (boost::xpressive::regex_search(str, rex))
        std::cout << "Match found." << std::endl;
    else
        std::cout << "No match found." << std::endl;
}

Prints "Match found." for me. If you want to find all the matches …

#include <iostream>
#include <string>
#include <boost/xpressive/xpressive_dynamic.hpp>

int main()
{
    std::string str = "foobarfoo";
    std::string rstr = "foo";
    boost::xpressive::sregex rex = boost::xpressive::sregex::compile(rstr);
    boost::xpressive::sregex_iterator it(str.begin(), str.end(), rex), end;

    for (; it != end; ++it )
        std::cout << "Match found at offset "
                  << ((*it)[0].first - str.begin())
                  << std::endl;
}

For me, this prints:

Match found at offset 0
Match found at offset 6