Clojure gets great performance with its immutable data structures, but no one pretends they're as fast as plain native java arrays or using mutation. It's norm

Clojure gets great performance with its immutable data structures, but no one pretends they're as fast as plain native java arrays or using mutation. It's normal in the Clojure community to drop down to using arrays or transients (http://clojure.org/transients http://clojure.org/transients) in high performance functions and then convert the result back to an immutable data structure. As long as you still present a pure interface, no one knows or cares what kind of mutation you do internally.