函数返回值

<aside> 🖤 没有明确定义返回值的函数，也有一个默认的返回值，类型为 Void，值为一个空元祖 ()。

</aside>

函数参数标签与参数名称

<aside> 👋 参数标签可以重名，但参数名称必须唯一。

</aside>

可变参数

<aside> 👩‍💻 可变参数在函数体内会被当作一个确定元素类型的数组，函数可以有多个可变参数，所以可变参数的第一个参数必须要有一个标签，用来表明为可变参数的起始元素。

</aside>

func arithmeticMean(_ numbers: Double..., with weights: Double...) -> (Double, Double) {
    var total: Double = 0
    for number in numbers {
        total += number
    }
    
    var weightTotal: Double = 0
    for weight in weights {
        weightTotal += weight
    }
    return (total / Double(numbers.count), weightTotal / Double(weights.count))
}
arithmeticMean(1, 2, 3, 4, 5, with: 3, 3, 3, 5, 5)

func swapTwoInts(_ a: inout Int, _ b: inout Int) {
    let temporaryA = a
    a = b
    b = temporaryA
}

var someInt = 3
var anotherInt = 107
swapTwoInts(&someInt, &anotherInt)
print("someInt is now \\(someInt), and anotherInt is now \\(anotherInt)")
// 打印“someInt is now 107, and anotherInt is now 3”

func arithmeticMean(_ numbers: Double..., with weights: Double...) -> (Double, Double) {
    var total: Double = 0
    for number in numbers {
        total += number
    }
    
    var weightTotal: Double = 0
    for weight in weights {
        weightTotal += weight
    }
    return (total / Double(numbers.count), weightTotal / Double(weights.count))
}

var a: Double = 1
var b: Double = 2
var c: Double = 3
var d: Double = 4
var e: Double = 5
arithmeticMean(a, b, c, d, e, with: a, b, c, d, e)