[Boost-users] [Regex] Accessing match count

Subject: [Boost-users] [Regex] Accessing match count
From: ninti_at_[hidden]
Date: 2010-03-10 08:01:25

Newbie here trying to reimplement PHP's preg_match_all() function in C++. I'm 
rewriting a PHP class which functions as a Porter Stemmer. I seem to have the 
regex_replace code working nicely but am now stuck on regex_match/regex_search. I 
want to count the number of times a regex matches within a string. 
The regex attempts to match all occurrences of one+ vowels followed by one+ 
consonants (known as 'm' or measure, roughly equivalent to a syllable). 
 
The original PHP function is as follows: 
 
private static function m($str) 
{ 
    $c = '(?:[bcdfghjklmnpqrstvwxz]|(?<=[aeiou])y|^y)'; 
    $v = '(?:[aeiou]|(?<![aeiou])y)'; 
 
    $str = preg_replace("#^$c+#", '', $str); 
    $str = preg_replace("#$v+$#", '', $str); 
     
    preg_match_all("#($v+$c+)#", $str, $matches); 
 
    return count($matches[1]); 
} 
 
So all I'm interested in here is the number of matches. I'm afraid I'm not even 
really sure which boost regex function I should be using, it seems like 
regex_search may be the correct choice as I'm not matching a whole string. This 
is what I've got so far: 
 
 
using namespace std; 
using namespace boost; 
 
string regex_vowel = "(?:[aeiou]|(?<![aeiou])y)"; 
string regex_consonant = "(?:[bcdfghjklmnpqrstvwxz]|(?<=[aeiou])y|^y)"; 
 
string get_m(string word) 
{ 
    regex c("^" + regex_consonant); 
    regex v(regex_vowel + "$"); 
    string replacement = ""; 
    word = regex_replace(word, c, replacement); 
    word = regex_replace(word, v, replacement); 
 
 
[ ... so far so good, this does the same as the first four lines of the PHP code 
above ... ] 
 
 
    string re = "(" + regex_vowel + "+" + regex_consonant + "+)"; 
    regex expression(re); 
 
    string::const_iterator start, end;  
    start = word.begin();  
    end = word.end();  
    match_results<string::const_iterator> what;  
    match_flag_type flags = match_default | match_partial;  
    regex_search(start, end, what, expression, flags); 
    string thing = what[1]; 
    int size = thing.size(); 
 
    cout <<  what[1] << endl; 
    string s; 
    stringstream out; 
    out << size; 
    s = out.str(); 
 
    return s; 
} 
 
This does not replicate the last two lines of PHP code above, instead returning 
the number of characters in a substring of sorts. So yes, I'm lost! Have tried 
several variations/possibilities but can't find a good example to work with. Have 
tried some much simpler variations they're not working either. 
 
TIA for any tips, even on which regex function I should be using. 
 
Mick