gistfile1.rb

module RefineInteger
  refine Fixnum do
    def /(other)
      case other
      when Integer
        Rational(self, other)
      else
        super
      end
    end
  end
end

module Rationalized
  p 1 / 2  #=> 0

  using RefineInteger

  p 1 / 2  #=> (1/2)
end