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(new Iterator[List[Int]] {
  def hasNext: Boolean = ???
  def next(): List[Int] = ???
}).flatten

给出错误：

value flatten is not a member of Iterator[List[Int]]
[error] possible cause: maybe a semicolon is missing before `value flatten'?
[error]     }.flatten
[error]       ^
[error] one error found

但

(new Iterator[List[Int]] {
  def hasNext: Boolean = ???
  def next(): List[Int] = ???
}: Iterator[List[Int]]).flatten

作品。还将迭代器存储在 val 中。

斯卡拉版本：2.11.8

给出以下代码

sealed trait Fruit

case class Apple(color: String) extends Fruit
case class Orange(color: String) extends Fruit

def getAppleColor(apple: Apple) = apple.color
def getOrangeColor(orange: Orange) = orange.color

val myMap: Map[String, Fruit] = Map(
"myApple" -> Apple("red"),
"myOrange" -> Orange("orange"),
)

val myMapOfFunctions: Map[String, Apple with Orange => String]  = Map(
"myAppleColorFun" -> getAppleColor,
"myOrangeColorFun" -> getOrangeColor,
)

为什么myMapOfFunctions不是 aMap[String, Fruit => String]类似于myMap？我想是因为它与功能有关，但我想更好地理解原因。谢谢！