For anyone curious as to what ARC is in this context (not the dialect of Lisp HN is written in): <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Automatic_Reference_Counting" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Automatic_Reference_Counting</a><p>Last time I did any Objective-C you had to retain&#x2F;release yourself so the auto stuff is interesting. As far as I can tell the benefit over Garbage Collection is that GC only works well when you have lots of excess spare memory, which is constrained on mobile devices.