Haskell - Control.Applicative.Alternative 有什么用？
我正在查看 Haskell 库中的 Applicative 类，并偶然发现了 替代。
这门课有什么用？谷歌搜索没有发现任何特别有见地的东西。它似乎完全不合适，因为它与 Applicative 包捆绑在一起。
有人可以发布一个您将使用此类的可能场景吗？
I was looking at the Applicative class within Haskell libraries and stumbled across Alternative.
What is this class good for? A google search did not reveal anything particularly insightful. And it seems to be completely out of place, bundled as it is with the Applicative package.
Could someone please post a possible scenario where you would use this class?
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它通常与解析器组合器一起使用。例如，如果
space是匹配单个空白字符的解析器组合器，则many space将是匹配连续空白的组合器。不过，我同意它在
Control.Applicative中有点不合适。It's commonly used with parser combinators. For example, if
spaceis a parser combinator that matches a single whitespace character,many spacewould be one that would match consecutive whitespace.I can agree that it's slightly out of place in
Control.Applicative, though.有时
<|>运算符非常有用：Sometimes the
<|>operator is quite useful: