要理解递归，首先必须理解递归。
To understand recursion, one must first understand recursion.
子贡说：“贫穷却不阿谀奉承，富贵却不狂妄自大，怎样？”孔子说：“可以。不如穷得有志气，富得有涵养的人。”子贡说：“修养的完善，如同玉器的加工：切了再磋，琢了再磨，对吧？”孔子说：“子贡啊，现在可以与你谈诗了。说到过去，你就知道未来。”
The best experiments often come from simple ideas and careful observation.
The anointed don't like to talk about painful trade-offs. They like to talk about happy "solutions” that get rid of the whole problem- at least in their imagination.
