// 函数嵌套:函数作用域中定义了另外一个函数,内层函数的作用域中可以使用外层函数的参数
func helloLanou(var num: Int){
    num++
    func hello23(){
        num++
    }
    hello23()
    num
}

helloLanou(10)


func hellolanou2() -> ((Int) -> String) { func hanshu (i:Int) -> String
    {
        return "\(i)"
    }
    return hanshu
}

hellolanou2()
let hanshu = hellolanou2()
let i = hanshu(1)

// 声明一个函数,实现功能:传入"+","-","*","/"的字符串,返回对应运算的函数:"+"-----返回int + int = int

func jjcc (str:String) -> ((Int,Int) -> Int)? { func jjcc1 (num1:Int,num2:Int) -> Int {
        return num1 + num2
    }
    func jjcc2 (num1:Int,num2:Int) -> Int {
        return num1 - num2
    }
    func jjcc3 (num1:Int,num2:Int) -> Int {
        return num1 * num2
    }
    func jjcc4 (num1:Int,num2:Int) -> Int {
        return num1 / num2
    }
    switch str {
    case "+":
        return jjcc1
    case "-":
        return jjcc2
    case "*":
        return jjcc3
    case "/":
        return jjcc4
    default:
        return nil
    }

}


jjcc("+")
let func1 = jjcc("+")
let func2 = func1!(1,2)

// 函数的返回值是函数,可以用函数嵌套的形式实现,但是并不是必须使用函数嵌套

func func2(str:String) -> ((Int,Int) -> Int){ func resultFunc(num1:Int,num2:Int) -> Int{
        switch str {
        case "+":
            return num1 + num2
        case "-":
            return num1 - num2
        case "*":
            return num1 * num2
        case "/":
            return num1 / num2
        default:
            return 0
        }
    }
    return resultFunc
}

// 指定类型别名
typealias funcType = ((Int,Int) -> Int) func func3 () -> funcType {
    func hanshu3 (num1:Int,num2:Int) -> Int {
        return  0
    }
    return hanshu3
}