# File rexml/xpath_parser.rb, line 572
  def join( arg1, op, arg2=nil)
			return nil unless arg1 and op
			op, arg2 = arg2, op unless arg2
			arg2 = [arg2] unless arg2.kind_of? Array
			if arg1.size == arg2.size
				arg1.each_index { |ind| arg1[ind] = yield(arg1[ind], op, arg2[ind]) }
			else
				arg1.collect! { |item| yield(item, op, arg2[0]) }
			end
			arg1
		end