Evolution of a Haskell programmer

and here's a working link to the original "Evolution of a programmer":

http://www.lri.fr/~filliatr/evolution

Damn, I read that and didn't understand half of the graduate stuff. Then again, I'm at work so what am I doing reading this? I have so much to learn and so little time to do it.

I like the 2nd junior version best.

    fac 0 = 1
    fac n = n * fac (n-1)