在Scala中，是否有办法将两个列表转换成Map? [英] In Scala, is there a way to take convert two lists into a Map?

问题描述

我有两个列表，一个List[A]和List[B].我想要的是Map[A,B]，但我想要zip的语义.所以开始像这样:

I have a two lists, a List[A] and a List[B]. What I want is a Map[A,B] but I want the semantics of zip. So started out like so:

var tuplesOfAB = listOfA zip listOfB

现在我不确定如何从我的tuplesOfAB构造一个Map.

Now I'm not sure how to construct a Map from my tuplesOfAB.

作为后续问题，我还想反转地图，以便从Map[A,B]创建一个Map[B,A].有人可以用线索棒打我吗?

As a follow-up question, I also want to invert my map so that from a Map[A,B] I can create a Map[B,A]. Can anyone hit me with a clue-stick?

推荐答案

在 2.8 中，使用CanBuildFrom功能(

In 2.8 this is really simple using the CanBuildFrom functionality (as described by Daniel) and using breakOut with a type instruction to the compiler as to what the result type should be:

import scala.collection.breakOut
val m = (listA zip listB)(breakOut): Map[A,B]

以下内容也可以工作:

val n: Map[A,B] = (listA zip listB)(breakOut)

并且(如下面的EastSun所指出的那样)，该代码已作为toMap

And (as EastSun, below, has pointed out) this has been added to the library as toMap

val o = (listA zip listB).toMap

关于反转地图，您可以执行以下操作:

As for reversing the map, you can do:

val r = m.map(_.swap)(breakOut): Map[B, A]

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