It never occurred to me that they'd be using tagged pointers for Objective-C runtime stuff. Of course it's obviously a good idea, but only after hearing it does it become so. Objective-C is always more dynamic than you think it is, so taking implementation cues from other dynamic language runtimes makes perfect sense.

It appears that they've been using tagged pointers on the desktop since 10.7, which I never realized: http://objectivistc.tumblr.com/post/7872364181/tagged-pointe...