Thanks a lot John for this, I changed my code to this and it worked.. boost::smatch what; while (boost::regex_search(startOffset ,endOffset , what, expression)) { int32 pos = what.position(); int32 len = what.length(); } However, could you tell me how to do this if my input string is "Hello World, Hello". that is the reason I am using a while loop instead of an if since my input string can contain more than 1 search string. Subhash On Tue, Mar 8, 2011 at 4:40 PM, John Maddock wrote:

I am new to boost Libraries and I am trying to find a substring using

...

Boost::Regex

Lets say I want to find string "Hello" in "Hello world".

std::string completeStr = "Hello World"; std::string::const_iterator startOffset = completeStr.begin(); std::string::const_iterator endOffset = completeStr.end();

std::string searchWord= "Hello"; boost::regex expression(searchWord);

boost::match_flag_type flags = boost::match_any; while(boost::regex_search(startOffset, endOffset, what, expression, flags)) { int32 position = what.position(1); int32 len = what[1].length(); }

but value of this position and length value is coming out to be -1. It is not able to find this substring, Could anyone tell me what I am doing wrong ?

First off, you don't need to use "match_any" unless it's what you really mean.

You're then accessing *marked subexpression 1* inside the loop, but the regular expression *does not contain any marked subexpressions*.

Use what.position() and what.length() to access the position and length info of the match as a whole.

HTH, John. _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users