Clojure isn't very slow. It's possible to write Clojure with identical performance of java (though this isn't idiomatic, and avoids some of Clojure's nicer feat

Clojure isn't very slow. It's possible to write Clojure with identical performance of java (though this isn't idiomatic, and avoids some of Clojure's nicer features). Clojure's immutable datastructures are ~25% slower than standard java, but also eliminate entire classes of bugs. I'm not familiar with Haskell's immutable data structures, but I'd be very surprised if there's an optimization that hasn't been adopted by Clojure. Rich Hickey put a lot of work into optimizing them.