[Boost-users] metaprogramming exercise 2-0

I just finished the first exercise in the C++ meta programming book. Then I checked what had been done before on this mailing list. Here is my solution: using namespace boost; template struct add_const_ref_impl { typedef T const & type; }; template <typename T> struct add_const_ref_impl { typedef T type; }; template<class T> struct add_const_ref { typedef typename add_const_ref_impl::type type; }; From Bruce Trask comes: using namespace boost; template<typename T> struct add_const_ref { typedef typename add_reference::type type; }; His solution is SO much better then mine. However, when I first saw it I thought it must be wrong because I assumed that add_const on a reference would would return a const reference. In other words, the code below would be false: bool a = is_same::type, int &>::value; However! bool "a" is true. So my question is why is "a" true? Why isn't add_const::type == int const &? Thanks, Chris