Getting index of matched pattern in Boost::regex

[dearvivekkumar]

I need to get the index at which the pattern is found while iterating through each loop.

I tried with distance but I am getting compile time error.

Is it possibe? If yes, What will be best way to get it??

void test2()
{
	std::string text = "I am <single angle bracket> trying to use [single square bracket] [[double square bracket]] Boost::regex library. <single angle bracket>";
	std::string::const_iterator start = text.begin();
	std::string::const_iterator end = text.end();


	boost::regex pattern("((<.*?>)|(\\[.*?\\]))");
	boost::smatch what;
	boost::match_flag_type flags = boost::match_default;

	try
	{
		if(boost::regex_search(text, what, pattern))
		{

			for(unsigned i = 0; i < what.size(); ++i)
			{
				std::cout << what[i] << std::endl;
			}
			
			// update search position:
			start = what[0].second;
			//std::cout << std::distance(start, end);
			
			// update flags: 
			flags |= boost::match_prev_avail;
			flags |= boost::match_not_bob;
		}
	}
	catch(std::runtime_error ex)
	{
	}	
}

Also any advice for improving this code will be very helpful to me.
Thanks