Scala:可遍历的foreach定义 [英] Scala: Traversable foreach definition

问题描述

我想 Traversable 特性中的 foreach 方法定义如下:

I suppose foreach method in Traversable trait is defined as follows:

def foreach[U](f: Elem => U)

应将其定义为 foreach [U，Elem](f:Elem => U)，因为有两种类型， Elem 和 U 吗?

Should it be defined as foreach[U,Elem](f:Elem =>U) as there are two types, Elem and U ?

推荐答案

foreach [U](A => U)是特征 Traversable [+ A] .

trait Traversable[+A] extends TraversableLike[A, ...] {
  ...
}

trait TraversableLike[+A, ...] extends ... {
  ...

  def foreach[U](f: A => U): Unit

  ...
}

https://github.com/scala/scala/blob/2.12.x/​​src/library/scala/collection/TraversableLike.scala#L124

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