class Foo
	def initialize x
		if x>0
			def positive
			end
		else
			def negative
			end
		end
	end
end
f = Foo.new 1
f.positive  class Foo
  def initialize x
    if x>0
       define_singleton_method(:positive) { puts 'positive' }
    else
       define_singleton_method(:negative) { puts 'negative' }
    end
  end
end