Taming Friends for Use in Templates

any design patterns and programming idioms rely on the use of friend declarations. However, when friend declarations are used in templates, the obfuscated syntax can bewilder even expert programmers. This month's solution demonstrates how to fine-tune friend declarations, while overcoming the syntax barrier at the same time.

How do you declare a template as a friend of another template? How can you distinguish between a specialization and a primary template in such declarations? What if you need to declare an asymmetric overloaded operator as a friend?

Follow the guidelines and rules set forth in this solution.