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STL regex to match multiple substrings

hansaaa (115)
Hi, I am using the (fairly) new STL implementation, which I just became aware of, of regexes. Seems to be an implementation of boost::regex ;)

Anyway, I have code, which I would like to use to get ALL matches within a string.

My String is: "Unseen University - Ankh-Morpork"

My regex is (simply): "Un" ;)

using code:

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const char *reg_esp = "Un";


std::regex rgx(reg_esp);
                       
std::cmatch matches;
const char *target = "Unseen University - Ankh-Morpork";
 

if (std::regex_search(target, matches, rgx)) {
    
 
    const size_t n = matches.size();
    for (size_t a = 0; a < n; a++) {
        std::string str (matches[a].first, matches[a].second);
        std::cout << str << "\n";
    }
}


gives output:

"Un" (one line only). How do I get this to match ALL instances of "Un" (i.e. that the output is "Un\nUn", i.e Un two times)?

Cheers for any and all help!! :)

hansaaa :)
Cubbi (4774)
Each call to regex_search() generates one match. To get more than one, either call it in a loop, or use a regex iterator:

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#include <regex>
#include <iostream>
#include <cstring>

int main()
{
    std::regex rgx("Un");
    const char *target = "Unseen University - Ankh-Morpork";
    for(auto it = std::cregex_iterator(target, target + std::strlen(target), rgx);
             it != std::cregex_iterator();
           ++it)
    {
        std::cmatch match = *it;
        std::cout << match.str() << '\n';
    }
}
 
Un
Un


Works with clang++/libc++, but liveworkspace is down at the moment, so I can't demo. Note that this won't work with GCC, where regex is not implemented so you have to use boost.regex if that's your platform.
Last edited on
hansaaa (115)
Ok,that should work! Thanks! :)
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