Ruby flew too

Reproducing the Elo rating algorithm in Ruby is a little challenge that I took upon myself recently for a small hack. The same Elo rating system that was scrawled upon the glass in "The Social Network" as the algorithm that Mark Zuckerberg used on rank people on FaceMash. As an exercise, here's a pass at it with a little BDD thrown in for good measure. A new file - elo.rb: require 'minitest/spec' require 'minitest/autorun' describe "result" do describe "when both players start with rating of 100 and k factor of 30" do it "must return 115 for the winner" do new_rating.must_equal 115 end end end Starting a new algorithm is always tricky. We know that the Elo rating system is essentially concerned with assigning ratings to players based on the outcome of their games or matches. In fact, it is widely used as a chess ranking algorithm. At a first glance then, I thought I might want to jump in and start mo...

Ruby has, at its root, an Object. Methods available in Object are available to every class because every class in Ruby inherits from Object somewhere in its own class hierarchy. Of course, you can override methods in subclasses, changing the functionality of a root method. You might stumble on to this idea if you work through Test Driven Development By Example by Kent Beck, translating the Java code into Ruby as you go. At some point pretty early on, he overrides the equality method on the Currency class to better test if two instances are equal. I'm going to do the same here, working with Instruments instead of Currency. Equality Equality in Ruby can be expressed using any of the following three methods object == other equal?(other) eql?(other) These methods are defined on the base Object. The default implementation of equality will only return true if both objects are exactly the same. The interesting thing is that although these three methods start out functioning the...