具有多个子类型的Scala通用（元组）类型 [英] Scala generic (tuple) type with multiple subtypes

问题描述

我正在Scala中编写一个数据结构（基本上是一个HashMap），它将采用一个元组（每次可能有不同数量的参数）并对其进行处理。为了一般地实现这个，我定义了一个类型：

  type T <：Tuple1 [_] with Tuple2 [_，_]带有Tuple5 [_，_，_，_，_]的Tuple3 [_，_，_]与Tuple4 [_，_，_，_] 
  

然后是数据结构

  val map = new HashMap [Int，T ] 
  

但这很丑陋，因为每次必须处理更多参数在一个元组中。是否有定义一个通用的元组类型？

谢谢，
YK

解决方案

第一个解决方案是使用 Product ，如@ om-nom-nom所述。确实，它是所有元组中唯一的超类型。

  val map = Map.empty [Int，Product] 
 map +（2  - >（a，b））
  

然后使用方法 productArity ， productElement 和 productIterator 来处理返回值。

您也可以使用列表（或任何索引集合）的地图。

  val map = Map.empty [Int，List [_]] 
 map +（3  - >（a::b::c:: Nil）） 
 map +（2  - > List（a，b））
  

最后的解决方案对用户来说并不方便，但至少您确切知道您处理的是什么样的集合。您也可以添加一个隐式。

I am writing a data structure (basically a hashmap) in Scala that will take one tuple (of possibly different number of arguments each time) and do something with it. To generically implement this, I defined a type:

type T <: Tuple1[_] with Tuple2[_,_] with Tuple3[_,_,_] with Tuple4[_,_,_,_] with Tuple5[_,_,_,_,_]

and then the data structure

val map = new HashMap[Int, T]

But this is ugly, since I have to change the type every time I have to handle more arguments in a tuple. Is there to define a generic tuple type?

Thanks, Y.K.

解决方案

The first solution is to use Product, as said by @om-nom-nom. Indeed, it's the only common supertype of all tuples.

val map = Map.empty[Int, Product]
map + (2 -> ("a", "b"))

And then to use the methods productArity, productElement and productIterator to handle the returned value.

You can also use a map of list (or any indexed collection).

val map = Map.empty[Int, List[_]]
map + (3 -> ("a" :: "b" :: "c" :: Nil))
map + (2 -> List("a", "b"))

The last solution is not that convenient for the user, but at least you know exactly what collection you handle. You could also add an implicit.

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