RSSFeedGenerator and RSSFeedParser are computation files to be use with an awesome distributed stream processor framework(http://www.concord.io/)
RSSFeedGenerator is responsible for crawling http://www.craigslist.org/about/best/all/index[0-5000+].rss and filtering for url+summary then send it over to RSSFeedParser.
RSSFeedParser searches the summary for "free" string then sends the url to the logger. It is not much of a parser, but it demonstrates how to use the streaming framework.
See http://docs.concord.io/ for detail on creating computation file for Concord.