super - How can I redefine Fixnum's + (plus) method in Ruby and keep original + functionality?

Question

This throws me a SystemStackError in 1.9.2 Ruby (but works in Rubinius):

class Fixnum
  def +(other)
   self + other * 2
  end
end

but there is no super for + (based on other errors).

How can I access the original + functionality?

Answer 1

Use alias_method. Alias Fixnum's + to something else, then refer to it in the new +:

class Fixnum
  alias_method :old_add, :+
  def +(other)
    self.old_add(other) * 2
  end
end