On 7/25/05, David Abrahams <dave@boost-consulting.com> wrote:
Why not use zip_iterator?
zip_iterator doesn't do what I want. From the documentation: "The zip iterator provides the ability to parallel-iterate over several controlled sequences simultaneously. A zip iterator is constructed from a tuple of iterators. Moving the zip iterator moves all the iterators in parallel. Dereferencing the zip iterator returns a tuple that contains the results of dereferencing the individual iterators." For example, if I had two sequences {1,2} and {10,20} and I used a zip_iterator to iterate through them, I would get (1,10) and (2,20). This can be verified by compiling and executing the following short program: #include <boost/iterator/zip_iterator.hpp> #include <boost/tuple/tuple.hpp> #include <iostream> #include <vector> int main() { typedef std::vector<int> IntSeq; // a = {1,2} IntSeq a; a.push_back(1); a.push_back(2); // b = {10,20} IntSeq b; b.push_back(10); b.push_back(20); typedef boost::zip_iterator< boost::tuples::tuple< IntSeq::const_iterator, IntSeq::const_iterator> > ZIt; ZIt cur(boost::make_tuple(a.begin(), b.begin())); ZIt end(boost::make_tuple(a.end(), b.end())); for ( ; cur != end; ++cur ) { std::cout << "{ " << boost::tuples::get<0>(*cur) << ", " << boost::tuples::get<1>(*cur) << " }" << std::endl; } return 0; } The iterator that I am proposing would provide the sequence (1,10), (2,10), (1,20), (2,20). Alex