Sub-classing Fixnum in ruby

Question

So I understand you aren\'t supposed to to directly subclass Fixnum, Float or Integer, as they don\'t have a #new method. Using DelegateClass seems to work though, but is it

Answer 1

Could you not extend FixNum itself? Like...

class Fixnum
  def even?
    self % 2 == 0
  end
end

42.even?