Kernel is "mostly" just lexical unless you explicitly opt-out with FEXPRs. FEXPRs are what draw most people into Kernel. However, what is probably more import

Kernel is "mostly" just lexical unless you explicitly opt-out with FEXPRs. FEXPRs are what draw most people into Kernel. However, what is probably more important but doesn't immediately stick out until you poke at Kernel a lot harder are the fully reified "environments". "Environments are copy on write that don't destroy older references" has very subtle consequences that seem to make dynamic scope a lot better behaved. This also has the consequence that I can force things to explicitly evaluate in reference to the "ground environment" which is an explicit signal that it can always be compiled. I suspect there is a lot of fertile research ground here. In addition, there is a lot of implementation subtlety that I'm not sure he really grasped. Environments need a special data structure otherwise they cons up an enormous amount of garbage (I suspect it really needs a Bitmapped Vector Trie like Clojure). I wish Shutt were still around to talk to. :(