Rich Hickey says during talks that Clojure's persistent data structures are based on this book and inspired by the Haskell implementation. The book is in Hickey

Rich Hickey says during talks that Clojure's persistent data structures are based on this book and inspired by the Haskell implementation. The book is in Hickey's recommended reading list. Language designers should pursue the books in that list; it's a good one. http://www.amazon.com/Clojure-Bookshelf/lm/R3LG3ZBZS4GCTH http://www.amazon.com/Clojure-Bookshelf/lm/R3LG3ZBZS4GCTH The main Clojure ('JClojure') implementation has these written in Java but Clojurescript has a pure Clojure implementation and there are Clojure-in-Clojure projects that do the same. The Java versions are still slightly faster on the JVM, unless things have changed. Clojure does not require you to program in pure functional style like Haskell. You can even write Clojure code with no immutable data structures and always use the Java paradigm data structures instead, though I do not recommend it. The support for mixing both paradigms and also transactional memory are part of the defining flexibility of Clojure. It's not a bondage and discipline affair; Clojure has a strong aesthetic but you can code however you want when you need to. I think Scala has similar data structures, also.