Building a simple reactive programming framework

You have gained an understanding of what reactive programming means in a theoretical way. Now, we're going to get very concrete and build a simple reactive programming system, then build a demo so we can watch it in action. The roots of formalized reactive programming are in statically typed languages, particularly C#. That's of little concern to us as users of a language based around dynamic typing, but it does mean that the standard presentation of these ideas is heavily intertwined with types, templates, interfaces, and anonymous functions. We'll be a little less Pythonic here and perhaps a little more C#-ish. That said, let's move on to the coding.

Observers

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