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What is the best way to obtain a simple, efficient immutable queue data type in Clojure?
It only needs two operations, enqueue and dequeue with the usual semantics.
I considered lists and vectors of course, but I understand that they have comparatively poor performance (i.e. O(n) or worse) for modifications at the end and beginning respectively – so not ideal for queues!
Ideally I’d like a proper persistent data structure with O(log n) for both enqueue and dequeue operations.
Problem solved – solution for others who may find it helpful.
I’ve found that Clojure has the clojure.lang.PersistentQueue class that does what is needed.
You can create an instance like this:
As far as I can see, you currently need to use the Java interop to create the instance but as Michal helpfully pointed out you can use peek, pop and conj subsequently.