在 Anti-XML 中压缩拉链 [英] Zipping zippers in Anti-XML

问题描述

在这个问题中，提问者想要这样转换文档:

In this question, the asker wants to transform documents like this:

<text>
  The capitals of Bolivia are <blank/> and <blank/>.
</text>

进入这个:

<text>
  The capitals of Bolivia are <input name="blank.1"> and <input name="blank.2">.
</text>

正如我在我的回答中所指出的，Anti-XML 的zippers 提供了一个这个问题的干净解决方案.例如，以下内容适用于重命名空白元素:

As I noted in my answer there, Anti-XML's zippers provide a clean solution to this problem. The following, for example, would work for renaming the blank elements:

import com.codecommit.antixml._

val q = <text>The capitals of Bolivia are <blank/> and <blank/>.</text>.convert

(q \\ "blank").map(_.copy(name = "input")).unselect

很遗憾，以下方法不起作用:

Unfortunately the following doesn't work:

(q \\ "blank").zipWithIndex.map { case (el, i) => el.copy(
  name = "input",
  attrs = Attributes("name" -> "blank.%d".format(i + 1))
)}.unselect

当然，因为一旦我们对拉链进行了 zipWithIndex-ed，我们就不再有拉链，只有一个 IndexedSeq——我们不能有 Zipper[(Node, Int)] 因为定义是 trait Zipper[+A <: Node] ....

Because of course once we've zipWithIndex-ed the zipper we no longer have a zipper, just an IndexedSeq—we can't have a Zipper[(Node, Int)] because the definition is trait Zipper[+A <: Node] ....

是否有一种干净的方法可以在 Anti-XML 拉链上使用 zip 或 zipWithIndex，使用 map 等进行一些其他操作?，最后得到的东西仍然是拉链?

Is there a clean way to use zip or zipWithIndex on an Anti-XML zipper, do some other operations with map, etc., and end up with something that's still a zipper?

推荐答案

我想不出一种直接的方法来实现你所需要的，但是如果你愿意去使用一个较低级别的功能，你可以使用一个折叠，例如:

I can't think of a direct way to achieve what you need, but if you're willing to go for a lower level function, you can use a fold, e.g.:

val blanks = q \\ "blank"

(0 until blanks.size).foldLeft(blanks) {case (z, i) => z.updated(i, z(i).copy(
  name = "input",
  attrs = Attributes("name" -> "blank.%d".format(i + 1)))
)}.unselect

请注意，zipper 是一个随机访问容器，因此在这种情况下效率应该不是问题.

Note that the zipper is a random access container, so efficiency shouldn't be an issue in this case.

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