我可以在Scala中压缩两个以上的列表吗？ [英] Can I zip more than two lists together in Scala?

问题描述

  val l = List（List（a1，b1，c1 ），列表（a2，b2，c2），列表（a3，b3，c3））
  

我怎样才能得到：

  List（（a1，a2 ，a3），（b1，b2，b3），（c1，c2，c3））
  

由于zip只能用于组合两个列表，我认为您需要以某种方式迭代/减少主列表。毫不奇怪，以下内容不起作用：

  scala> l reduceLeft（（a，b）=> a b）b）
< console>：6：error：type mismatch; 
 found：List [（String，String）] 
 required：List [String] 
l reduceLeft（（a，b）=> a zip b）
  

任何建议一个如何做到这一点？我认为我错过了一个很简单的方法。

更新：我正在寻找一个可以接受List的N列表中包含M个元素，并创建一个M TupleNs列表。

更新2：事实证明，用例有一个列表列表，而不是一个元组列表，所以我接受南瓜的回应。它也是最简单的，因为它使用本地方法。

解决方案

我不相信有可能生成一个列表任意大小的元组，但转置功能完全符合您的需求，如果您不介意取得列表清单。

Given the following Scala List:

val l = List(List("a1", "b1", "c1"), List("a2", "b2", "c2"), List("a3", "b3", "c3"))

How can I get:

List(("a1", "a2", "a3"), ("b1", "b2", "b3"), ("c1", "c2", "c3"))

Since zip can only be used to combine two Lists, I think you would need to iterate/reduce the main List somehow. Not surprisingly, the following doesn't work:

scala> l reduceLeft ((a, b) => a zip b)
<console>:6: error: type mismatch;
 found   : List[(String, String)]
 required: List[String]
       l reduceLeft ((a, b) => a zip b)

Any suggestions one how to do this? I think I'm missing a very simple way to do it.

Update: I'm looking for a solution that can take a List of N Lists with M elements each and create a List of M TupleNs.

Update 2: As it turns out it is better for my specific use-case to have a list of lists, rather than a list of tuples, so I am accepting pumpkin's response. It is also the simplest, as it uses a native method.

解决方案

I don't believe it's possible to generate a list of tuples of arbitrary size, but the transpose function does exactly what you need if you don't mind getting a list of lists instead.

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