1.多个返回值

    func x(x:Int, y:Int)->(Int, Int){
        let a = x+y
        let b = x-y
        return (a, b)
    }
    let (a, b) = x(10, y: 3)
    print("a = \(a)")
    let val = x(10, y: 3)
    print("val = \(val.0)")    func x(x:Int, y:Int)->(Int, Int){