Swift 区间运算符 笔记

... or ..<

// 闭区间
for index  in 1 ... 5 {
    print("闭区间 is index = \(index)")
}
print("=================")

/*
 闭区间 is index = 1
 闭区间 is index = 2
 闭区间 is index = 3
 闭区间 is index = 4
 闭区间 is index = 5
 */

//半闭区间
for index  in 1 ..< 5 {
    print("半闭区间 is index = \(index)")
}
print("=================")
/*
 半闭区间 is index = 1
 半闭区间 is index = 2
 半闭区间 is index = 3
 半闭区间 is index = 4
 */

//单侧区间

//闭区间有另外一种形式来让区间朝一个方向尽可能的远——比如过，一个包含数组所有元素的区间，从索引 2 到数组的结束。在这种情况下，你可以省略区间运算符一侧的值。因为运算符只有一侧有值，所以这种区间叫做单侧区间

let names = ["Anna", "Alex", "Brian", "Jack"]

for name in names[2...] {
    print(name)
}
/*
 Brian
 Jack
 */
print("=================")
for name in names[...2] {
    print(name)
}
/*
 Anna
 Alex
 Brian
 */
print("=================")

for name in names[..<2] {
    print(name)
}
/*
 Anna
 Alex
 */
print("=================")

let range = ...5
range.contains(7)   // false
range.contains(4)   // true
range.contains(-1)  // true