template with friend function problem

[Martin v. Loewis]

> What is wrong with my instantiation of friend functions?

In C++, at the point of instantiation, the definition of a template
function (or class) must be visible - just having the declaration is
not enough. As a result, you must define the template implementation
in the header file. This is most easily achieved by #including
Vector.C into Vector.h.

Hope this helps,
Martin