Lisp dialects like Clojure have a very rich set of algorithms that can present altered views on containers without modifying data in the underlying container. This is very important in functional languages as data is immutable and returning copies of containers is costly despite the containers being optimised for copy-on-write. Having these algorithms available prevents unnecessary data copies. While I am not going into mutating algorithms in this post, the tradition of non-modifying alghorithms…