此代码片段中紧跟在“new”关键字之后的 cons“::”运算符的含义是什么？

Question

I'm studying Scala and see in a tutorial the following definition. There are 3 " :: ". My understanding is that the first " :: " is a method in class List , and the third " :: " is a class name.

But I cannot understand the meaning of the second " :: ".

sealed abstract class List {
  def ::(head: Int): List = new ::(head, this)
}
case object Nil extends List
case class ::(head: Int, tail: List) extends List

Answer 1

new ClassName ( constructorArguments ) creates a new instance of the class ClassName , passing the constructorArguments as constructor arguments.

In your example, :: is the class-name, and head and this are the constructor arguments.

(See https://docs.scala-lang.org/tour/classes.html for more information about constructors.)