The main problem is probably creating and traversing the strings, although I have not benchmarked it. This version https://gist.github.com/Codas/894694eea247aaa

The main problem is probably creating and traversing the strings, although I have not benchmarked it. This version https://gist.github.com/Codas/894694eea247aaacf35f https://gist.github.com/Codas/894694eea247aaacf35f runs about 4 times faster than the python version on my machine. It does use some libraries that are not in the haskell platform though.