Mark Flamer
I have also become intrigued and confused by this "category theory" and how it relates to Haskell. It has been stated many times that you don't need to understand category theory to utilize the Haskell language but all the concepts, patterns and every paper describing them seems to be written by someone who understands it. It really appears that to "innovate" in this community it helps to at least have a basic understanding of the theory. I have started working through this book "Conceptual Mathematics, A first introduction to categories" and so far it seems very understandable and interesting for mere mortals like myself.
My experience is that you can very well innovate in this community without understanding anything of category theory (CT). The fun starts when you realize that your concept, when sound, can most often be expressed in the categorical framework, and if not, then your concept is either unsound or can be improved by CT. In other words, you can learn it along the way, and you do that best by writing software and using well designed libraries. For understanding CT itself my suggestion is that you don't try too hard. The human mind is used to visualizing things, and except for an abstract directed graph this fails terribly for CT. That means, when you feel stuck, chances are that's just a false feeling. Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad.