scala case类问题 [英] scala case classes questions

问题描述

我有两个关于'::'案例类的问题。

I have two questions regarding the '::' case class.

::可以用作

case head :: tail => ...

它是如何工作的？意思，什么是Scala用来匹配List实例与:: case类的流程？假设我有一个类MyClass，使用operator op，我可以创建一个名为op的case类，我可以使用：

How does it work? Meaning, what is exactly the flow that Scala uses to match a List instance with the :: case class? Given that I have a class MyClass, with operator op, can I create a case class named op that I can use as:

case foo op bar => ....

？

推荐答案

     scala> abstract class Stack {
     |     def push(n :Int):Stack
     | }
      defined class Stack

     scala> final case class push(st :Stack,hd :Int) extends Stack {
     |     override def push(n :Int):Stack = new push(this,n)
     | }
     defined class push

     scala> object NullStack extends Stack {
     |     override def push(n :Int):Stack = new push(null,n)
     | }
     defined module NullStack

     scala> val s = NullStack.push(1).push(2)
     s: Stack = push(push(null,1),2)

     scala> def test(s :Stack) = s match { case st push i => println(st +"push " + i) }
     test: (Stack)Unit

     scala> test(s)
     push(null,1)push 2

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