C++ regex_match doesn't match

Question

I'm using C++ on XCode. I'd like to match non-alphabet characters using regex_match but seem to be having difficulty:

#include <iostream>
#include <regex>

using namespace std;

int main(int argc, const char * argv[])
{
    cout << "BY-WORD: " << regex_match("BY-WORD", regex("[^a-zA-Z]")) << endl;
    cout << "BYEWORD: " << regex_match("BYEWORD", regex("[^a-zA-Z]")) << endl;

    return 0;
}

which returns:

BY-WORD: 0
BYEWORD: 0

I want "BY-WORD" to be matched (because of the hyphen), but regex_match returns a 0 for both tests.

I confoosed.

Collin · Accepted Answer · 2014-04-29 15:00:29Z

2

regex_match tries to match the whole input string against the regular expression you provide. Since your expression would only match a single character, it will always come back false on those inputs.

You probably want regex_search instead.

answered Apr 29, 2014 at 15:00

Collin

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jfly · Accepted Answer · 2014-04-29 15:05:58Z

2

regex_match() returns whether the target sequence matches the regular expression rgx. If you want to search the non-alphabet characters from the target sequence, you need regex_search():

#include <regex>
#include <iostream>
int main()
{
    std::regex rx("[^a-zA-Z]");
    std::smatch res;
    std::string str("BY-WORD");
    while (std::regex_search (str,res,rx)) {
        std::cout <<res[0] << std::endl;
        str = res.suffix().str();
    }

}

answered Apr 29, 2014 at 15:05

jfly

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