在 Scala 中使用幻像类型标记原始类型 [英] Marking primitive types with phantom types in Scala

问题描述

在 Scala 中，我可以使用幻像类型的概念(例如 此处) 来标记类型并在运行时删除此信息.我想知道是否可以用幻影类型标记原始类型而不将它们装箱.

In Scala I can use the concept of phantom types (as described e.g. here) to mark types and have this information erased at runtime. I wonder whether it is possible to mark primitive types with phantom types without having them boxed.

一个例子可以是一个函数，它只让 Int 是素数时才通过.签名可能类似于以下内容:

An example could be a function that lets an Int only pass if it is a prime. The signature might look similar to the following:

def filterPrime(i: Int): Option[Int with IsPrime]

函数返回值 Some(i) 如果 i 是质数或 None 否则.

The function returns the value Some(i) if i is prime or None else.

上述想法是否可以在 Scala 中实现而无需对原始整数进行装箱?

Is the stated idea possible to implement in Scala without boxing the primitive integer?

推荐答案

以下对我有用:

trait IsPrime
val x = 5.asInstanceOf[Int with IsPrime]
val y:Int = x

val z:Int with IsPrime = 6 /* this line causes a compile error
                              which is what you want */

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