1  public class Foo   2  {   3      private int val;   4   5      public Foo(int val)   6      {   7          this.val = val;   8      }   9  10      public static bool operator==(Foo lhs, Foo rhs)  11      {  12          return lhs.val == rhs.val;  13      }  14  15      public static bool operator!=(Foo lhs, Foo rhs)  16      {  17          return ! (lhs == rhs);  18      }  19  }  

where the != operator just negates a call to ==. You would repeat this process for the other two pairs if you wanted to provide them. (And yes, I know if you provide your own == then you have to also provide a GetHashCode method.) There is no reason that the developer should have to do anything more than provide a comparison operator and then let the system define the other methods in terms of that comparison...

And that's exactly what Ruby does. If you include the module called "Comparable" in your class, and provide a comparison method called <=> (called the "spaceship method" because that's what it looks like) then you get ==, !=, <, <=, > and >= for free! That's right, by defining one method you get six defined in terms of it automatically. Now that's how it should be done! Which results in code like this:

   1  class Foo   2      include Comparable  # Here's where the majic starts   3   4      attr_accessor :val   5   6      def initialize(val)   7          self.val = val   8      end   9  10      # comparison method; all others defined in terms of this  11      def <=>(other)  12          val <=> other.val  13      end  14  end  

Obviously these are both trivial classes but I think you get the point. There is no reason why you should have to define more than one method to get all the normal comparisons that you would expect in a language.