C++ Primer Plus

Template Classes and Friends

Template class declarations can have friends, too. You can classify friends of templates into three categories:

• Non-template friends

• Bound template friends, meaning the type of the friend is determined by the type of the class when a class is instantiated

• Unbound template friends, meaning that all specializations of the friend are friends to each specialization of the class

Let’s look at examples of each.

Non-Template Friend Functions to Template Classes

Let’s declare an ordinary function in a template class as a friend:

template <class T>class HasFriend{public:    friend void counts();     // friend to all HasFriend instantiations    ...};

This declaration makes the counts() function a friend to all possible ...