[aredington]

One of Clojure's fundamental opinions, asserted by the language eagerly, is that vector quantities should be treated as values the way scalar quantities are in most languages. Specifically, this means that when you operate with a list and append to it, instead of modifying the value of the next (cdr) pointer in the last node, you create a new list and return the new list as the result of the append operation. These immutable collections afford certain classes of algorithm that destructively modified ones do not. Rich reviews this concept pretty well here: http://www.infoq.com/presentations/Value-Values

This story doesn't spend much time discussing this particular opinion of Clojure's or why you would choose to circumvent it by making a mutable linked list. Additionally by virtue of skipping the immutability discussion, it fails to discuss how append to the head of a list is crucially different from append to the tail when working with data structurally sharing underlying data.

Additionally it prefers to define an interface over a protocol (using definterface instead of defprotocol), and it uses camelCase naming instead of Clojure's culturally embraced hyphen-cased naming.

In short this describes a way to build a data structure in Clojure, but is not a particularly good as an example to be followed of how you should build data structures in Clojure. johnwalker cited a couple more idiomatic examples, e.g. data.finger-trees: https://github.com/clojure/data.finger-tree/blob/master/src/...