import UIKit

var greeting = "Hello, playground"

//: [Previous](@previous)

//: ## 区间运算符

//: ### 闭区间运算符
/*:
    闭区间运算符：
        a...b : a <= 取值 <= b
 */

let names = ["Anna", "Alex", "Brian", "Jack"]
for i in 0...3 {
    print(names[i])
}

let a = 1
var b = 3
for i in a...b {
    print(names[i])
}

let range = 1...3
for i in range {
    print(names[i])
}



// i默认是let，有时需要声明为var
for var i in 1...3 {
    // i的值可以发生变化
    i += 5
    print(i)
}

// 用不上变量,可以用_进行忽略
for _ in 1...3 {
    print("123456")
}

//: ### 半开区间运算符
/*:
    半开区间运算符
        a..<b : a <= 取值 < b
 */

 
//: ### 单侧区间运算符
/*:
    单侧区间运算符
        a... : a <= 取值
        ...b : 取值 <= b
 */


//: ### 区间类型
// 闭区间 ClosedRange
let range1: ClosedRange<Int> = 1...3
// 半开区间 Range
let range2: Range<Int> = 1..<3
// 单侧区间 PartialRangeThrough
let range3: PartialRangeThrough<Int> = ...5


//: ### 带间隔的区间值
// 使用函数stride
for tickMark in stride(from: 4, to: 11, by: 2) {
    print(tickMark)
}


//: ## switch
/*:
    switch注意点
    - switch必须保证能处理所有的情况
    - 能处理所有情况的下，可以省略default
    - switch 也支持Character、String类型
    - switch 支持区间匹配以及元组匹配
 */

// 默认可以不写break，并不会贯穿到后面的条件
var num = 1
switch num {
case 1:
    print("number is 1")
case 2:
    print("number is 2")
default:
    print("number is other")
}

// 使用fallthrough可以实现贯穿效果
var number = 1
switch number {
case 1:
    print("number is 1")
    fallthrough
case 2:
    print("number is 2")
default:
    print("number is other")
}

//: #### 区间匹配
let count = 62
switch count {
case 0:
    print("none")
case 1..<5:
    print ("a few")
case 5..<12:
    print("several")
case 12..<100:
    print("dozens of")
case 100..<1000:
    print("hundreds of")
default:
    print("many")
} // dozens of




//: #### 元组匹配
// 可以使用下划线_ 忽略某个值
let point = (1, 1)
switch point {
case (0, 0):
    print("the origin")
case (_, 0):
    print ("on the x-axis")
case (0, _):
    print("on the y-axis")
case (-2...2, -2...2):
    print("inside the box")
default:
    print( "outside of the box")
}

//: ### 值绑定
// 必要时 let 可以换为 var
let point1 = (2, 0)
switch point1 {
case (let x, 0):
    print("on the x-axis with a x value of \(x)")
case (0, let y):
    print("on the y-axis with a y value of \(y)")
case let(x, y):
    print("somewhere else at (\(x), \(y))")
}

//: ### where
// 1. 用在case的后边
let point2 = (1, -1)
switch point2 {
case let(x, y) where x == y:
    print("on the line x == y")
case let(x, y) where x == -y:
    print("on the line x == -y")
case let(x, y):
    print("somewhere else at (\(x), \(y))")
}

//2. 对数据进行过虑
var numbers = [10, 20, 30, -10, -30]
var sum = 0
for num in numbers where num > 0 {
    sum += num;
}
print(sum)

//: ### 标签语句
// 标签语句是
//    标签: 代码
outer: for i in 1...4 {
    for k in 1...4 {
        if k == 3 {
            continue outer
        }
        
        if i == 3 {
            break outer
        }
        
        print("i == \(i), k == \(k)")
    }
}


//: [Next](@next)