swift - 什么是 Swift 中的多次序列？

Question

我正在查看 this language来自 Swift GeneratorType 文档，我很难理解它:

Any code that uses multiple generators (or for...in loops) over a single sequence should have static knowledge that the specific sequence is multi-pass, either because its concrete type is known or because it is constrained to CollectionType. Also, the generators must be obtained by distinct calls to the sequence's generate() method, rather than by copying.

“多次通过”序列是什么意思？这种语言似乎很重要，但我找不到很好的解释。例如，我了解“多 channel 编译器”的概念，但我不确定这些概念是否相似或相关...

此外，我还搜索了其他回答此问题的帖子。我找到了 this one ，它在 C++ 上下文中进行了以下语句:

The difference between algorithms that copy their iterators and those that do not is that the former are termed "multipass" algorithms, and require their iterator type to satisfy ForwardIterator, while the latter are single-pass and only require InputIterator.

但我也不完全清楚它的含义，我不确定这个概念在 Swift 中是否相同。

任何比我聪明的人的见解都将不胜感激。

Answer 1

“多遍”序列是可以通过 for...in 循环或使用任意数量的生成器(通过 generate() 构建)迭代多次的序列)

文本解释了你会知道一个序列是多遍的，因为你

• 知道它的类型(可能是你设计的类)或
• 知道它符合CollectionType。 (例如，集合和数组)