Add Comparing Class Hierarchy Relationships as a Ruby til.

README.md

@@ -71,6 +71,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 ### ruby
 
 - [Are They All True?](ruby/are-they-all-true.md)
+- [Comparing Class Hierarchy Relationships](ruby/comparing-class-hierarchy-relationships.md)
 - [Create an Array of Stringed Numbers](ruby/create-an-array-of-stringed-numbers.md)
 - [Destructuring Arrays In Blocks](ruby/destructuring-arrays-in-blocks.md)
 - [Disassemble Some Codes](ruby/disassemble-some-codes.md)

ruby/comparing-class-hierarchy-relationships.md

@@ -0,0 +1,27 @@
+# Comparing Class Hierarchy Relationships
+
+The comparator methods (`<`,`>`, etc.) can be useful for a lot of things. In
+Ruby, they can be used to compare classes in order to understand how they
+relate to one another on the class hierarchy.
+
+```ruby
+# Fixnum is a subclass of Integer
+> Fixnum < Integer
+=> true
+# Integer is not a subclass of Fixnum
+> Integer < Fixnum
+=> false
+# Fixnum and String are not related to one another
+> Fixnum < String
+=> nil
+```
+
+The `<` operator will tell you if there is a subclass relationship. The `>`
+operator will tell you if there is an ancestor relationship. When `nil`
+results, it means the two classes do not have a direct relationship.
+
+There are a few more of [these types of
+operators](http://ruby-doc.org/core-2.2.2/Module.html#method-i-3C) on the
+Module class.
+
+[source](http://kerrizor.com/blog/2015/05/14/serendipity-and-ruby-objects/)