Hi people, A couple years ago I wrote a container indexed by type, which I've come to consider a basic building block for reusable code. Effectively, code can use "type_maps" to handle an arbitrary structure, without needing to know member identifiers, and gets the speed benefit of compile-time access resolution. A simple implementation follows: namespace NS { namespace Private { class no_type2 { }; class no_type3 { }; class no_type4 { }; class no_type5 { }; template <typename T> class type_map_base { public: void operator=(const T& t) { t_ = t; } operator const T&() const { return t_; } private: T t_; }; template<> class type_map_base<no_type2> { }; template<> class type_map_base<no_type3> { }; template<> class type_map_base<no_type4> { }; template<> class type_map_base<no_type5> { }; } template <typename T1, typename T2 = Private::no_type2, typename T3 = Private::no_type3, typename T4 = Private::no_type4, typename T5 = Private::no_type5> class type_map : public Private::type_map_base<T1>, public Private::type_map_base<T2>, public Private::type_map_base<T3>, public Private::type_map_base<T4>, public Private::type_map_base<T5> { public: using Private::type_map_base<T1>::operator=; using Private::type_map_base<T2>::operator=; using Private::type_map_base<T3>::operator=; using Private::type_map_base<T4>::operator=; using Private::type_map_base<T5>::operator=; }; } // sample usage... #include <iostream> #include <string> using namespace std; int main() { NS::type_map<int, string> tmid; tmid = 3; tmid = "hello"; string s = tmid; cout << (int)tmid << ' ' << (string)tmid << ' ' << s << endl; cout << sizeof(tmid) << " vs " << sizeof(int) << '+' << sizeof(string) << endl; } I've found typemaps useful for writing things like a logging system that allows arbitrary criterion for cataloging errors. To store several data items of the same type, simply wrap each instance in a distinct class (possibly using the template w/ unique number idiom). Implementation note: the empty base class optimisation makes it practical to have a single template, avoiding typelists (mpl sequences), preprocessing etc.. Cheers, Tony ___________________________________________________________ How much free photo storage do you get? Store your holiday snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com