Some object-oriented languages won't let you subclass the  data types
like integers. Other languages implement those data types as classes, so you
can subclass them, no questions asked. Ruby implements numbers as classes
(Integer, with its concrete subclasses Fixnum and Bignum), and you can subclass
those classes. If you try, though, you'll quickly discover that your subclasses
are useless: they don't have constructors.  

Ruby jealously guards the creation of new Integer objects. This way it ensures
that, for instance, there can be only one Fixnum instance for a given number

The easiest way to delegate all methods is to create a class that's nearly empty
and define a method_missing method.