I'm not very good at explaining the things in short, but I'll try.
Hi there, thanks for the explanation. I think I got it and it was not as bad as you maybe think. To come back to the initial problem of string tokenizing. I am trying to implement the finder in terms of ForwardIteratorT. Here is what I think I am expecting to do - also actually I am not very sure about it. I justed started to read M. Austern's book and I am quite new to concepts, requirements and so on. So here is what I did so far: struct comment_finder { template<typename ForwardIteratorT> boost::iterator_range<ForwardIteratorT> operator()( ForwardIteratorT Begin, ForwardIteratorT End ) { ForwardIteratorT first, last; while ( Begin != End ) { first = Begin; if ( *Begin++ == '/' && *Begin == '/' ) { last = first; while ( *last++ != '\n' ) { // FAILURE: Return an empty range if ( last == End ) return boost::make_range( ??, ?? ); // return an empty range - HOW? } // SUCCESS: Return the range return boost::make_range( first, last + 1 ); } } return boost::make_range( ??, ?? ); // return an empty range - HOW? } }; Is this the way I have to implement the finder or can it be implemented using some facilities in your library? This implementation is quite low-level, so I am wondering if this is correct. Secondly, for the case this is correct, how should I return an empty range or what shall I return if didn't find a matching range? What are the following steps? Do I have to split two time times or how do I erase the comments out of the string? Will the final token iterator be only of ForwardIteratorT or will be of the type of the conatiner that is holding the tokens. ( e.g. for a vector it would be a randow access iterator? ) Sorry for the inconvinience and thanks for the help so far. -Dirk