Nil compared with Numeric and String

compared.rb

  # Allows `nil` to compare to String,Numeric,NilClass.So you can sort a array if it include nil.
  # 
  #   nil <=> ''			# =>  0
  #   nil <=> 'Tom'   # =>  -1
  #   nil == ''       # false
  #   For the NilClass the method == do not depond on the <=>.
  #
  #   '' <=> nil 			# =>  0
  #   'Tom' <=> nil   # => 1
  #   '' > nil        # => false
  #   'a' > nil       # => true
  #   '' == nil       # => false
  #   For the String the methods <,<=,>=,> depend on <=>,but the method == does not depend on <=>.
  #   
  #   1 == nil        # => false
  #   1 <=> nil       # => 1
  #   
  #   ['c',nil,'a','b'].sort # => [nil, "a", "b", "c"]
  #   [2,nil,1,3,-2].sort # => [-2, nil, 1, 2, 3]
  #   
  # CREDIT: u2
  #
  # @deprecated It's not a good idea!
  # It have some side effects.
  # ['c',nil,'a','b'].sort_by{|i|i.to_s}
  # => [nil, "a", "b", "c"]

class NilClass
  def <=>(b)
	alias compared <=>
    case b.class.name
    when 'String' then ''<=>(b)
    when 'Float','Fixnum','Bignum' then 0<=>(b)
    when 'NilClass' then 0
    else
      compared(b)
    end
  end

end

class String
	alias compared <=>
	def <=>(b)
		if b.is_a? NilClass
			compared('')
		else
			compared(b)
		end
	end
end

[Fixnum,Float,Bignum].each do |numeric|
	numeric.class_eval do
		alias compared <=>
		def <=>(b)
			if b.is_a? NilClass
				compared(0)
			else
				compared(b)
			end
		end
	end
end