C++14 variable template with default template parameter?

Question

C++14 will allow variable templates:

template <typename T> constexpr T pi = T(3.1415926535897932385);

Now consider the following case:

template <typename T = double> constexpr T pi = T(3.1415926535897932385);

Question: how do I get pi with the default parameter ?

pi; // Option 1 (I hope...)
pi<>; // Option 2

Answer 1

Based on n3651 I would say pi<>;. In the current standard template argument deduction, which being able to do pi is a form of, only applies to functions. Since the paper mentions absolutely nothing about TAD it is unlikely they would use it.