# File lib/amazon/shoppingcart.rb, line 232
    def modify_items(item_list, quantity)

      check_minimum_quantity(quantity, 0)

      # If quantity is zero, use remove_items instead, as Amazon's 'modify'
      # operation can't handle removal.
      return remove_items(item_list) if quantity == 0

      url = AWS_PREFIX + "?ShoppingCart=modify&f=xml&dev-t=%s&t=%s&sims=true"
      url = url % [@token, @id]

      item_list = [item_list] if item_list.is_a? String

      item_list.each { |item| url << "&Item.%s=%s" % [item, quantity] }

      url = check_cart(url)

      @page = search(url)
      parse
    end