Iterator API (Syntax)

• Tree iterators should be Bidirectional Iterators (exception: Levelorder is Forward)
• Restrict access to data (especially pointers!)
• Make external algorithms object-based, i.e., operate on object through public interface
• Allow stopping in mid-traversal
• Allow multiple iterators for a single container
• Model: List <T>

Iterator Semantics

Preorder, Inorder, Postorder, Levelorder