I try to make stream-cons & stream-cdr using boost.proto & boost.fusion. code is here http://d.hatena.ne.jp/niitsuma/20110323/1300850731 But this is not work in the following case auto s= stream_cons(2,stream_cons(1,0)); auto ss= stream_cons(3, s); std::cout << proto_force( proto_force(ss.cdr.car).cdr.car).car << std::endl; //not work std::cout << stream_cdr(stream_cdr(ss)).car << std::endl; //not work Where is problem?