Editing Functional programming (section)

===Data structures===
{{main|Purely functional data structure}}
Purely functional [[data structure]]s are often represented in a different way to their [[imperative programming|imperative]] counterparts.<ref>[http://www.cambridge.org/us/academic/subjects/computer-science/algorithmics-complexity-computer-algebra-and-computational-g/purely-functional-data-structures ''Purely functional data structures''] by [[Chris Okasaki]], [[Cambridge University Press]], 1998, {{ISBN|0-521-66350-4}}</ref> For example, the [[array data structure|array]] with constant access and update times is a basic component of most imperative languages, and many imperative data-structures, such as the [[hash table]] and [[binary heap]],  are based on arrays. Arrays can be replaced by [[Map (computer science)|maps]] or random access lists, which admit purely functional implementation, but have [[logarithm]]ic access and update times. Purely functional data structures have [[Persistent data structure|persistence]], a property of keeping previous versions of the data structure unmodified. In Clojure, persistent data structures are used as functional alternatives to their imperative counterparts. Persistent vectors, for example, use trees for partial updating. Calling the insert method will result in some but not all nodes being created.<ref>{{Cite web|url=http://www.hypirion.com/musings/understanding-persistent-vector-pt-1|title=polymatheia - Understanding Clojure's Persistent Vector, pt. 1 |last=L’orange |first=Jean Niklas |website=Polymatheia |access-date=2018-11-13}}</ref>