[Haskell-begin] Morphing Endo (ICFP Contest 2007)

Did any of you tried to do a Haskell implementation of the ICFPC 2007 problem? I was thinking of using it as a learning exercise, but I am afraid of the stack. My approach is: 1) use Data.ByteString.Lazy.Char8 to read the contents of the DNA file 2) create a recursive function process::ByteString -> a that will call itself. I have a few problems: a) the DNA is 8MB long. How can I ensure the stack will hold a recursive call? b) there is an "abnormal ending" function called finish that is called anywhere in the code. Is it a good approach to return Empty to end processing? c) should I go "monadic", keeping the dna on a state monad? Thanks -- Rafael Gustavo da Cunha Pereira Pinto Electronic Engineer, MSc.