Clojure - datatypes - what I like about Clojure: pragmatic and compact solutions for typical programming problems. Clojure 1.2 will introduce the possibility of having better descriptions of data structures with functionalities defined on them. And not some monstrous construction like CLOS or other Lisp-OO extensions, but rather lean constructs that also fit well with the host environments (JVM and CLR). Looks quite interesting. The downside of all the changes in Clojure: books become outdated faster than they can be printed ...