Unexpected result in parsing a regular expression

From: abhinkar (abhinkar_at_[hidden])
Date: 2002-10-24 22:54:11

Hi,

I recently downloaded the boost regex library and am trying to use 
the search and replace (regex_merge) API. But I am not getting the 
expected result.

Here is what I am trying to do. I am trying to replace a single 
quoted string with something. But, the catch here is that the string 
in single quotes can have zero or many 2 consecutive single quotes. 
For example:

Input (Ignore the angle brackets>:
<foo='string with '' consecutive '' single ''quotes' bar='string 
with no single quotes'>
To be replaced by 'XXX'. So the output that I want:
<foo=XXX bar=XXX>

Here is the regular expression that I wrote in Perl:
/(\'[^']*(\'\')*[^']*\')/

I get the expected result in Perl. 

So, to test this with regex library I wrote a sample program to use 
the regex_merge API and try the replace functionality. 
---------------------------replace.cc--------------------------------
#include <boost/regex.hpp>
#include <string>
#include <iostream>
#include <sstream>    
#include <iterator>

using namespace std;
using namespace boost;

const std::string formatstr("XXX");

std::string processexp(string resp)
{
   regex expression("(\'[^']*(\'\')*[^']*\')");
   std::string result;
   std::ostringstream t;
   std::ostream_iterator<char, char> oi(t);   
   cout << "Response:" << resp << endl;
   result = boost::regex_merge(resp, expression, formatstr, 
boost::format_all);
   return result;
}

int main(int argc)
{
   std::string res;

   res = processexp("foo='string with '' consecutive '' 
single ''quotes' bar='string with no single quotes'");
   cout << "results=" << res << endl;
   return 0;
}
---------------------------------------------------------------------
The output I get is:
foo=REPLACEDREPLACED bar=REPLACED

I tried several ways, but couldn't get the regular expression to 
work to return the expected result.

I WOULD really appreciate if someone could help me.

Thanks in advance,

Sameer