Hi The docs: http://www.boost.org/doc/libs/1_47_0/libs/fusion/doc/html/fusion/adapted/std... seem to suggest that one can pipe an adapted std::pair 'directly' to cout. I find the following though: #include <iostream> #include <boost/fusion/adapted.hpp> // adapt pair. #include <boost/fusion/sequence.hpp> // operator<<() ? #include <boost/fusion/container.hpp> // as_vector int main(int argc, char** argv) { std::pair<std::string, int> p("foo", 7); std::cout << p << std::endl; // does not compile although docs suggest it should. std::cout << boost::fusion::as_vector(p) << std::endl; // compiles and works as expected. return 0; } Am I missing an include? Is sending to cout without first using as_vector actually supported? Daniel