// Playground - noun: a place where people can playimport UIKit// For-In 循环// 1 遍历数字区间for index in 1...5 {    println("\(index) times 5 is \(index)")}// 2 遍历数组let names = ["Anna", "Alex", "Brain", "Jack"]for name in names {    println("hello, \(name)")}// 3 遍历字典let numberOfLegs = ["spider" : 8, "ant" : 6, "cat" : 4]for (name, legCount) in numberOfLegs {    println("\(name) has \(legCount) legs")}// 4 遍历字符for character in "hello" {    println(character)}// For 循环for var index = 0; index < 3; index++ {    println("index is \(index)")}// While do-whilevar i = 0do {    i++} while (i < 3)while (i < 5) {    i++}// 条件语句 Conditional Statementsvar temperatureInFahrenheit = 30if temperatureInFahrenheit <= 32 {    println("It‘s very cold")}switch temperatureInFahrenheit {    case 1...20:        println("1...20")    case 23, 30:        println("come here")        fallthrough // 默认不会进入下一个判断，加上这个关键字可以让匹配直接进入下一个    default:        println("default")        break // 跳出switch}var somePoint = (1, 1)switch somePoint {    case let (x, y) where x == y:        println("equal")    default:        break}