for-loop - For-in循环动态闭域

Question

动态近距离for-in的正确方法是什么？环形？我在这部分遇到错误for z in 1...[10-x]{

for x in 1...10{

    for y in 1...x{
        print(" ")
    }

    for z in 1...[10-x]{
        print("*")
    }

    println()

}

错误:

Playground execution failed: <EXPR>:26:15: error: 'ClosedInterval<T>' does not have a member named 'Generator' for z in 1...[10-x]{

Answer 1

[10-x]表示一个数组(带有单个元素 10-x )。你会想要“正常” 括号:

for z in 1 ... (10 - x) { ... }

或者只是

for z in 1 ... 10 - x { ... }

因为...优先级低于 - .

正如您所注意到的，这不适用于 x = 10因为范围为 end < start Swift 中不允许。

执行循环n你最好使用范围 0 ..< n使用省略上限值的范围运算符。这适用于 n = 0还有:

for x in 1 ... 10 {
    for y in 0 ..< x {
        print(" ")
    }
    for z in 0 ..< 10 - x {
        print("*")
    }
    println()
}