mop_18.rb

# shortcut method for opening a metaclass on the receiver
module Kernel;def m;class << self;self;end;end;end

Module.m # #<Class:Module>, metaclass of Module
Module.m.superclass # Class, because that is how Module is bootstrapped

Module.m.m # #<Class:#<Class:Module>>, metaclass of Module's metaclass
Module.m.superclass # #<Class:#<Class:Module>>
Module.m.m.superclass # #<Class:#<Class:Module>>
# Opening a metaclass on Module's metaclass changes its superclass to be the same as its metaclass's superclass!?

# the same behavior occurs at arbitarily deep meta-levels:
Object.m.superclass # Class
Object.m.m.superclass # #<Class:#<Class:Object>>
Object.m.superclass # #<Class:#<Class:Object>>
# opening a third metaclass modifies the superclass of 'm.m', but leaves 'm' alone
Object.m.m.m # #<Class:#<Class:#<Class:Object>>>
Object.m.m.superclass # #<Class:#<Class:#<Class:Object>>>
Object.m.m.m.superclass # #<Class:#<Class:#<Class:Object>>>
Object.m.superclass # #<Class:#<Class:Object>>

# same deal for regular old Object instances, vs. classes and modules
o = Object.new # #<Object:0x101168440>
o.m # #<Class:#<Object:0x101168440>>
o.m.superclass # #<Class:Object> (at this point the superclass is Object's metaclass)
o.m.m # #<Class:#<Class:#<Object:0x101168440>>> (meta-metaclass of o)
# ...and now the superclass of meta and the superclass of meta-meta are the same:
o.m.superclass # #<Class:#<Class:#<Object:0x101168440>>>
o.m.m.superclass # #<Class:#<Class:#<Object:0x101168440>>>