I have been told that you could pretty much literally implement the
algorithms from the problem specification with Seq from Data.Sequence and achieve acceptable speed (IIRC ~ one minute for generating a whole picture).
Yes, it is straightforward to implement the algorithm when using sequences.
Are you sure that there is no unintentional bug in your implementation that slows things down?
The test cases on the problem definition all worked, but they touch very little of the code. I added some "trace" calls, but could not see any trouble. I also did some runs "by hand" and it seemed ok. If only Gödel was wrong... :-) -- Rafael Gustavo da Cunha Pereira Pinto Electronic Engineer, MSc. -- Rafael Gustavo da Cunha Pereira Pinto Electronic Engineer, MSc.