It sometimes would be useful to have a template specialization be
itself a template.  For example, to define persistent I/O on all
vectors of type T, one could specialize PersistentIO<T>:

 template <class T>
 class PersistentIO< vector<T> >
 { ... };

I'd like to know whether this is allowed by the current draft.
Given the affirmative, what does the T argument represent inside
the specialization?

An alternative, which is not unfortunately not supported, would be
to define a specialization as a friend inside vector<T>:

 template <class T>
 class Vector<T> {
 public:
  // ...
  friend class PersistentIO< vector<T> >
  { ... };
 };

Could someone enlighten me as to why it is not permitted to define
a friend class inside another class, whereas defining a friend
inline function in a class is perfectly acceptable (and very useful
when used with templates)?

 Nicolas Chapados
 chapados@bnr.ca
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