[Haskell-cafe] Vector-like data structure

[Krzysztof Skrzętnicki]

Hi

I'm looking for a data structure with following characteristics:
1. O(1) lookup
2. O(1) modification
3. amortized O(1) append
4. O(1) size query

This roughly characterizes C++ vector<> class. I'm ready to implement
it myself, but first I would like to ask if anyone knows package with
similar data structure.
If there are many, which one would you choose and why?

Best regards

Christopher Skrzętnicki