Swift - 区间运算符（... 和 ..<）

1，闭区间运算符：a...b

for iCount in 10...100{
     //从10遍历到100（包括100）
}

 2，半闭区间运算符：a..<b

  var fruts = ["apple","orange","banana"]
        let iCount = fruts.count
        for i in 0 ..< iCount{
           print("第\(i+1)个水果是\(fruts[i])")
        }

 3，倒序循环

for i in (0..<10).reversed() {
    print(i)
}

 4，字符串范围也可以使用区间运算符

//字符串截取
        let words = "Hangge.com"
        
        //不使用区间运算符
        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 = words.substring(with: 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 = words.substring(with: range2)
        print(rangeStr2)

 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

所以我们可以用这个特性检查字符串里的字符是不是都是合法字符（比如是不是都是小写）

 let words = "Hangge.com"
        
        let interval = "a"..."z"
        for c in words.characters{
            if !interval.contains(String(c)){
                print("\(c)不是小写字母")
            }
        }