Yes, Clojure does have many purely functional data structures built in to its core. I don't know the precise implementations, or if they're written in Clojure o

Yes, Clojure does have many purely functional data structures built in to its core. I don't know the precise implementations, or if they're written in Clojure or Java, but I believe they're based on the work of Phil Bagwell. Every functional language implementation I know of has many of these data structures available as a library somewhere. You certainly could implement these data structures in Ruby, though it's likely they wouldn't mesh as well as in a more functional language. This Stackexchange answer has links to many papers if you're interested in more: http://cstheory.stackexchange.com/questions/1539/whats-new-in-purely-functional-data-structures-since-okasaki http://cstheory.stackexchange.com/questions/1539/whats-new-i...