I have the following program where I make_zip_iterator on 2 vector<int>::iterator's and am trying to pass a Phoenix expression to std::for_each on the iterator. I wrote a lazy version of tuple.get<N> for that purpose. I get a compile error because the phoenix functor only accepts references, whereas the tuple element seems to get passed by value. What am I doing wrong? Manjunath #include <iostream> #include <vector> #include <algorithm> #include <boost/iterator/zip_iterator.hpp> #include <boost/tuple/tuple.hpp> #include <boost/spirit/include/phoenix_core.hpp> #include <boost/spirit/include/phoenix_operator.hpp> #include <boost/spirit/include/phoenix_statement.hpp> #include <boost/spirit/include/phoenix_scope.hpp> #include <boost/spirit/home/phoenix/function/function.hpp> using namespace boost::phoenix; using namespace boost::phoenix::arg_names; using namespace boost::phoenix::local_names; using namespace std; namespace fusion = boost::fusion; struct print_tuple { void operator()(const boost::tuple<int&, int&>& t) const { cout << t.get<0>() << " " << t.get<1>() << "\n"; } }; struct get0_ { template<typename Arg> struct result { typedef int type; }; template<typename Arg> int operator()(Arg a1) const { return a1.get<0>(); } }; function<get0_> get0; int main() { vector<int> a(10), b(10); for(unsigned i=0, e=a.size(); i!=e; ++i) { a[i] = i; b[i] = i; } std::for_each(a.begin(), a.end(), cout << arg1); std::for_each(boost::make_zip_iterator(boost::make_tuple(a.begin(), b.begin())), boost::make_zip_iterator(boost::make_tuple(a.end(), b.end())), cout << get0(arg1)); }