O(1) circular buffer in haskell?

Question

I'm working on a small concept project in Haskell which requires a circular buffer. I've managed to create a buffer using arrays which has O(1) rotation, but of course requires O(N) for insertion/deletion. I've found an implementation using lists which appears to take O(1) for insertion and deletion, but since it maintains a left and right list, crossing a certain border when rotating will take O(N) time. In an imperative language, I could implement a doubly linked circular buffer with O(1) insertion, deletion, and rotation. I'm thinking this isn't possible in a purely functional language like Haskell, but I'd love to know if I'm wrong.

Answer 1

If you can deal with amortized O(1) operations, you could probably use either Data.Sequence from the containers package, or Data.Dequeue from the dequeue package. The former uses finger trees, while the latter uses the "Banker's Dequeue" from Okasaki's Purely Functional Data Structures (a prior version online here).