http://numbbbbb.github.io/the-swift-programming-language-in-chinese/chapter1/02_a_swift_tour.html
http://numbbbbb.github.io/the-swift-programming-language-in-chinese/chapter1/02_a_swift_tour.html,布布扣,bubuko.com
原文：http://www.cnblogs.com/mykaka/p/3784459.html
