Thanks for this- I'm actually writing a Python interpreter in Coffeescript right now, so the Norvig interpreter and this coffeescript version are a great reference to compare against!
There's some sloppiness in the code so don't look at it too closely: left-in console.log calls and window variables for debugging, a couple outdated comments. You can look to later commits for improvements if you're interested (note that the file gets renamed from lispy.coffee to sweet.coffee).
