&符號學習：
http://www.cnblogs.com/likeyu/archive/2012/03/08/2382879.html
http://www.infoq.com/cn/news/2008/02/to_proc-currying-ruby19
數組與循環：
http://fujinbing.iteye.com/blog/1126232
http://www.oschina.net/translate/guide-ruby-collections-part-arrays
http://www.oschina.net/translate/guide-ruby-collections-ii-hashes-sets-ranges