Thinking Functionally in Ruby [video]

Slides are at http://experthuman.com/files/thinking-functionally-in-ruby.p... if you'd prefer.

Apologies for the point in the video where I answer in the affirmative a question about whether foldr is "the same as" foldl over the reversed list. In the context of the example that's correct, but of course in general it's only true when the function is commutative.