Google re2 namedcapture, how to parse results in c++?

Question

using google re2 library for regex i haven't found a way to parse results, anywhere!

this is a short example

bool b_matches ;
string s_teststr = " aaaaa flickr bbbb";
RE2 re("(?P<flickr>flickr)|(?P<flixster>flixster)");
assert(re.ok()); // compiled; if not, see re.error();
b_matches = RE2::FullMatch(s_teststr, re);

  b_matches = RE2::FullMatch(s_teststr, re);

// then,
re.NumberOfCapturingGroups() //-> always give me 2

 re.CapturingGroupNames(); //-> give me a map with id -> name (with 2 elements)

re.NamedCapturingGroups() //-> give me a map with name -> id (with 2 elements)

what i have to do to know that only flickr has been matched ?

thank you,

Francesco

--- after some more testing i didn't have found a soltuion for the namedcapture, only way thing i have found working give me the extracted text and is this.

string s_teststr = "aaa  hello. crazy world bbb";
std::string word[margc];
RE2::Arg margv[margc];
RE2::Arg * margs[margc];
int match;
int i;

    for (i = 0; i < margc; i++) {
        margv[i] = &word[i];
        margs[i] = &margv[i];
    }
   string s_rematch = "((?P<a>hello\\.)(.*)(world))|(world)";
  match = RE2::PartialMatchN(s_teststr.c_str(), s_rematch.c_str(), margs, margc);
cout << "found res = " << match << endl;
  for (int i = 0; i < margc; i++) {
        cout << "arg[" << i << "] = " << word[i] << endl;
    }

-------- this will give me in output:

found res = 1 arg[0] = hello. crazy world arg[1] = hello. arg[2] = crazy arg[3] = world arg[4] =

to test with the second part of the string matching...

string s_rematch = "((?P<a>hello\\.d)(.*)(world))|(world)";

--- i get as output:

foudn res = 1 arg[0] = arg[1] = arg[2] = arg[3] = arg[4] = world

my problem is taht the name capture --> a <--- never come out and the output should be cleared (lowercase in case of insensitive match, removed from added compatibily chars,.. ) and processed again against a map because i don't have the named capture which give me the key instead of the value for this preg

got it! the only way i've found to get my named capture is to parse the resutls args and when string length is > 0 then search for the arg id into ---------------------------------------------------- const map<int, string>& m_RE_namedmap2 = re_compiled.CapturingGroupNames(); // -- id => name -------------------------------------- this give me the keyword corresponding to the id found , than i have to create a new map with key (found searching for the id into the map of CapturingGroupNames and with the value which is the string with length > 0 — Francesco

Unknown Unknown · Accepted Answer · 2011-04-26T14:33:23

You can pass in a string to be populated upon success. For example:

std::string matchedValue;

if (RE2::FullMatch(s_teststr, re, &matchedValue))
{
    if (matchedValue.empty())
    {
        //not flickr
    }
}
else
{
    // matchedValue.empty() == true
}

Google re2 namedcapture, how to parse results in c++?

1 Answers