Ruby the native implementation seems to hide all singleton classes in ancestor() call. But, JRuby 0.9.0 returns singleton classes.

1. The output of the following
2. script is different from that of
3. Ruby 1.8.4

class Object
def singleton
class<<self; self; end
end
end

class Person
end

class Employee < Person
end

puts Employee.singleton.ancestors().join("\n")

Output with JRuby 0.9.0 is as follows:

#<Class:Employee>
#<Class:Person>
#<Class:Object>
Class
Module
Object
Kernel

Output with Ruby 1.8.4 is as follows:

Class
Module
Object
Kernel