Question

If a pointer to an user defined type is passed as template argument to a template class, is it possible to get the class type of the argument?

template <class T> struct UserType {
    typedef T value_type;
    ...
};

int main () {
    typedef std::vector<UserType<double>*> vecType
    vecType vec;

    vecType::value_type::value_type m; //how to get the double here?

    return 0;
}

Answer 1

Use traits:

template <typename> struct ptr_traits {};
template <typename T> struct ptr_traits<T*>
{ typedef T value_type; };

ptr_traits<vecType::value_type>::value_type m;