Swift - 运算符重载和运算符函数

struct CenterPoint {
    var x = 0,y = 0
}
func + (left:CenterPoint,right:CenterPoint) -> CenterPoint {
    return CenterPoint.init(x: left.x + right.x, y: left.y + right.y)
}
func == (left:CenterPoint,right:CenterPoint) -> Bool {
    return (left.x == right.x) && (left.y == right.y)
}
func != (left:CenterPoint,right:CenterPoint) -> Bool {
    return !(left == right)
}
func += (left:inout CenterPoint,right:CenterPoint){
     left = left + right
    print(left)
}
class AreaViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = UIColor.white
        //1.0，闭区间运算符：a...b
        for icount in 512...1000 {
            print(icount)
        }
        //1.2，半闭区间运算符：a..<b
        var fruits = ["apple","orange","banana"]
        for i in 0..<fruits.count {
            print("i---\(fruits[i])")
        }
        fruits.append("Longan")
        
        //1.3，倒序循环
        for j in (0..<10).reversed() {
            print(j)
        }
        //1.4，字符串范围也可以使用区间运算符
        let words = "mujin.com"
        let index = words.index(words.startIndex, offsetBy: 4)
        let index2 = words.index(words.startIndex, offsetBy: 6)
        let range1 = Range(uncheckedBounds: (lower: index, upper: index2))
        let rangeStr1 = String(words[range1]) //ge
        print(rangeStr1)
        //使用区间运算符
        let range2 = words.index(words.startIndex, offsetBy: 4)..<words.index(words.startIndex, offsetBy: 6)
        let rangeStr2 = String(words[range2])
        print(rangeStr2)
        
        //1.5，区间运算符除了返回一个Range外，还可以接受Comparable的输入，返回ClosedInterval或HalfOpenInterval
        let interval = "a"..."z"
        for c in words {
            if !interval.contains(String(c)){
                print("\(c)不是小写字母")
            }
        }
        //通过 + 进行方法重载相加
        var point1 = CenterPoint.init(x: 2, y: 3)
        let point2 = CenterPoint.init(x: 4, y: 5)
        let point3 = point1 + point2
        print(point3)
        print(point1 == point2)
        print(point1 != point2)
        point1 += point2
    }