Hi HN. If you get some value out of these slides, great! But please, do me a favor: don't try too hard to construct a narrative from a stack of slides which:

a) represent about 15% of the actual semantic content of the presentation; and

b) are shaped by the consideration that there's a limit to how much code you can put on a slide and have it still be readable.

A lot of this material has been covered in more detail on my blog (http://avdi.org/devblog) For instance, I wrote a whole article about Maybe, NullObject, and the limits of the ability to make objects falsy here: http://avdi.org/devblog/2011/05/30/null-objects-and-falsines...