We don't care about the content of the node. The interesting part is how do you define the Node itself. struct Node<T> { Node<T> left; Node<T> right; };

We don't care about the content of the node. The interesting part is how do you define the Node itself. struct Node<T> { Node<T> left; Node<T> right; }; would obviously be the best choice (what I call in the article "raw value"). But it's not valid C++.