函数字面量可以在 Scala 中使用类型参数吗? [英] Can a function literal use type parameter in Scala?

问题描述

给定以下多态方法 removeAt 的定义:

def removeAt[T](n: Int, ts: Seq[T]): (Seq[T], T) = ???

如何声明一个类似 removeAt 的函数列表?函数字面量可以使用类型参数吗?

如何使以下内容可编译并能够包含 removeAt?

List[(Int, Seq[_]) =>(Seq[_], _)](removeAt)

更新:为什么下面的工作正常，所以我可以foreach遍历列表并执行函数?这正是我首先需要的.

val 解决方案 = Seq[(Int, Seq[Any]) =>(Seq[Any], Any)](删除在)

解决方案

博文 shapeless 中的一流多态函数值 (1 of 3) — Scala 中的函数值 似乎暗示在标准"Scala 中没有办法拥有多态函数值:><块引用>

我们可以有一流的单态函数值，我们可以有二等的多态方法，但我们不能有一流的多态函数值......至少我们不能用标准Scala 定义.

看起来我们需要一个像 shapeless 这样的库.

Given the following definition of a method removeAt that's polymorphic:

def removeAt[T](n: Int, ts: Seq[T]): (Seq[T], T) = ???

How can I declare a list of removeAt-like functions? Can a function literal use type parameter?

How can I make the following compilable and able to contain removeAt?

List[(Int, Seq[_]) => (Seq[_], _)](removeAt)

UPDATE: Why does the following work fine so I can foreach over the list and execute the functions? That's exactly what I needed in the first place.

val solutions = Seq[(Int, Seq[Any]) => (Seq[Any], Any)](
  removeAt
)

解决方案

The blog post First-class polymorphic function values in shapeless (1 of 3) — Function values in Scala seems to imply that there's no way in "standard" Scala to have polymorphic function values:

We can have first-class monomorphic function values and we can have second-class polymorphic methods, but we can't have first-class polymorphic function values ... at least we can't with the standard Scala definitions.

It looks like we need a library like shapeless.

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