[Boost-users] Re: metaprogramming exercise 2-0

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 &?

I thought the same thing at first but it makes senses when we compare a reference to a constant pointer. add_const::type would be int * const and not int const * const. You might also try the following : template <typename T> struct AC { typedef const T type; }; and then check the result of is_same, int&>::value. Under Visual C++ with default compilation setting AC struct will give a compilation warning when template argument is a reference : warning C4181: qualifier applied to reference type; ignored

Thanks,

Chris

Philippe