// 遍历区间，返回元素值
for index in 1...5 {
    print("(index) times 5 is (index * 5)")
}

// 循环区间，忽略元素值
for _ in 1...power {
    answer *= base
}

// 遍历数组
let names = ["Anna", "Alex", "Brian", "Jack"]
for name in names {
    print("Hello, (name)!")
}

// 遍历字典
let numberOfLegs = ["spider": 8, "ant": 6, "cat": 4]
for (animalName, legCount) in numberOfLegs {
    print("(animalName)s have (legCount) legs")
}

while square < finalSquare {
    // statements ...
}

// 类似其他语言的do-while语句
repeat {
    // statements ...
} while square < finalSquare

temperatureInFahrenheit = 90
if temperatureInFahrenheit <= 32 {
    print("It's very cold. Consider wearing a scarf.")
} else if temperatureInFahrenheit >= 86 {
    print("It's really warm. Don't forget to wear sunscreen.")
} else {
     print("It's not that cold. Wear a t-shirt.")
}

// person字典中存在key为name的元素时打印name元素值
guard let name = person["name"] else {
    return
}
print("Hello \(name)")

let someCharacter: Character = "z"
switch someCharacter {
case "a":
    print("The first letter of the alphabet")
// case "b": 打开注释后会有编译错误，不存在隐式贯穿
case "c","z":    // 复合匹配
    print("The last letter of the alphabet")
default:
    print("Some other character")
}

// case分支匹配区间
switch approximateCount {
case 0:
    naturalCount = "no"
case 1..<5:
    naturalCount = "a few"
default:
    naturalCount = "many"
}

// case分支匹配元组
let somePoint = (1, 1)
switch somePoint {
case (0, 0):  // 元组元素是值类型
    print("(0, 0) is at the origin")
case (_, 0):// 元组元素使用 _ 匹配所有任意值
    print("(\(somePoint.0), 0) is on the x-axis")
case (-2...2, -2...2): // 元组元素是区间类型
    print("(\(somePoint.0), \(somePoint.1)) is inside the box")
}

let yetAnotherPoint = (1, 1)
switch yetAnotherPoint {
case (let x, 0):
    print("on the x-axis with an x value of \(x)")
case let (x, y) where x == y: // 输出 "(1, -1) is on the line x == y"
    print("(\(x), \(y)) is on the line x == y")
case let (x, y):
    print("(\(x), \(y)) is just some arbitrary point")
}