Hi, all. boost::tuple provide a member template function get to gain a element of tuple, As following: #include "boost\tuple\tuple.hpp" using namespace boost; template<typename T> class TA{public: template<typename T1, typename T2> void testfun(T1 e1, T2 e2) { tuple<T1, T2> t1(e1, e2); //T1 _e1 = t1.template get<0>(); //works *T1 _e1 = t1.get<0>(); //works for boost::tuple* /* However, according c++98, t1.get<0>() seems to should be encounter a compilor error. *I want to known how boost::tuple avoid this compile error.* */ } }; int main() { int i=10; float f=10.5f; TA<char> obj; obj.testfun(i, f); return 0; } The above sample pass the compilation of gcc3.4.2 and gcc 4.2.4. *According to boost::tuple, I implement a new tuple by myself. as following: * (In fact, the following code is mostly extracted from boost::tuple. ) namespace testNS{ template<int N, class T> struct element { private: typedef typename T::tail_type Next; public: typedef typename element<N-1, Next>::type type; }; template<class T> struct element<0,T> { typedef typename T::head_type type; }; struct null_type{}; template<typename HT, typename TT> struct cons { typedef HT head_type; typedef TT tail_type; template <int N> typename element<N, cons<HT, TT> >::type *get()* { typedef typename element<N, cons<HT, TT> >::type RetType; return RetType(); } }; template<typename HT> struct cons<HT, null_type> { typedef HT head_type; typedef null_type tail_type; typedef cons<HT, null_type> self_type; //get(BOOST_EXPLICIT_TEMPLATE_NON_TYPE(int, N)) template <int N> typename element<N, self_type>::type *get()* { typedef typename element<N, cons<HT,null_type> >::type RetType; return RetType(); //return boost::tuples::get<N>(*this); } }; template <class T0, class T1, class T2> struct map_tuple_to_cons { typedef cons<T0, typename map_tuple_to_cons<T1, T2, null_type>::type > type; }; // The empty tuple is a null_type template <> struct map_tuple_to_cons<null_type, null_type, null_type> { typedef null_type type; }; template<typename T0, typename T1, typename T2=null_type> class Tuple; template<typename T0, typename T1, typename T2> class Tuple: public map_tuple_to_cons<T0, T1, T2>::type { public: typedef T0 E0T; typedef T1 E1T; typedef T2 E2T; Tuple(const E0T& e0, const E1T& e1) { } }; }//endof testNS using namespace testNS; template<typename T> class TA{public: template<typename T1, typename T2> void testfun(T1 e1, T2 e2) { Tuple<T1, T2> t1(e1, e2); //T1 _e1 = t1.template get<0>(); //works * T1 _e1 = t1.get<0>(); //encounter compilor error /* the gcc3.4.2 error message: syntax error before `;' token the gcc4.2.4 error message: error: expected primary-expression before ')' token error: invalid operands of types '<unresolved overloaded function type>' and 'int' to binary 'operator<' */* } }; int main() { int i=10; float f=10.5f; TA<char> obj; obj.testfun(i, f); return 0; } By the way, how can i get contact with boost::tuple author.? -- miss you!