Order of objects in NSSet and NSMutableSet

I wanted to accomplish couple of things with this post. One was to test the SyntaxHighlighter plugin for posting code here and two to explain what I observed in trying to use the NSMutableSet class in the third example of chapter 2 in code I have posted before.

Game AI Objective-C Chapter 2 Source

As promised here are the links to the chapter 2 examples of the Programming Game AI Example book. As mentioned earlier, I have tried my best to stay true to the original C++ code structure. Only in the third examples have I differed a little by using Objective-C properties. Couple of things to note about the third example. 

Programming Game AI Chapter 2

Continuing on from my introduction to this blog, Mat Buckland's book Programming Game AI by Example is excellent so far. His math and physics introductions are just enough for anybody to understand how important the subjects of math and physics are to game development. His introduction to game state engines as a precursor to Game AI and a creation of a FSM (Finite State Machine) with just a few lines of code with the West World Messaging example is both simple and very interesting. His website for the book has a snapshot of chapter 2 introduction and some of the code. One problem?