Checking type of parameter pack using enable_if

Question

Since there is a restriction on allowed non-type variadic templates, I am trying to write a function taking an arbitrary number of doubles using enable_if. In essen

Answer 1

Here is another (c++11) version (heavily inspired by the T.C.'s one above):

#include 

template 
struct are_all_convertible {
    constexpr static bool value = std::is_convertible::value &&
                                  are_all_convertible::value;
};

template 
struct are_all_convertible {
    constexpr static bool value = std::is_convertible::value;
};

template::value>::type>
foo(T... t){ /* code here */}