有可能“咖喱"吗? Scala中种类更多的类型? [英] Is it possible to "curry" higher-kinded types in Scala?

问题描述

假设我有一个具有两个类型参数的特征，例如

Let's suppose I have a trait with two type parameters, e.g.

trait Qux[A, B]

以及具有较高类型参数的另一个特征，例如

and another trait with a higher-kinded type parameter, e.g.

trait Turkle[C[_]]

我希望能够用固定值代替Qux的类型参数之一，以便可以将其用于参数化Turkle.

I'd like to be able to substitute a fixed value for one of the type parameters for Qux, so that it can be used to parametrize Turkle.

这是一个示例(在Scala中没有意义的代码！):

Here's an example (of code that doesn't make sense in Scala!):

trait Baz[A] extends Turkle[Qux[A, _]]

任何人都知道如何实现这种效果吗?

Anyone have any ideas how to achieve this effect?

推荐答案

Jason Zaugg提出了最简洁的方法:

Jason Zaugg came up with the most succinct way to do this:

trait Baz[A] extends Turkle[({type x[a]=Qux[A, a]})#x]

IntelliJ的Scala插件可以选择将其折叠为:

IntelliJ's Scala plugin will optionally collapse this to:

trait Baz[A] extends Turkle[x[a]=Qux[A, a]]

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