Scala Actors：如果react永不返回，为什么它必须处于循环状态{}，为什么while（true）不起作用？ [英] Scala Actors: if react never returns, why does it need to be in a loop{}, and why doesn't while(true) work?

问题描述

Scala Actor入门。 Scala网站说：

Just getting started on Scala Actors. The Scala website says:

使用 react 来等待
新消息（<$ c的基于事件的挂件）可以避免线程阻塞操作$ c>接收）。但是，需要支付
（通常很小）的价格：反应永不返回。

Thread-blocking operations can be avoided by using react to wait for new messages (the event-based pendant of receive). However, there is a (usually small) price to pay: react never returns.

。 ..

请注意，在 while 内使用反应循环不起作用！但是，由于循环是常见的
，因此它在 loop 函数的形式
中提供了特殊的库支持。可以这样使用：

Note that using react inside a while loop does not work! However, since loops are common there is special library support for it in form of a loop function. It can be used like this:

loop {
  react {
    case A => ...
    case B => ...
  }
}

我现在很困惑-似乎是矛盾的：

I'm now confused - there seems to be a contradiction:

a）如果 react 永不返回，那么将其置于循环中的意义何在？ ？

a) If react never returns, then what's the point of putting it in a loop?

b）由于循环重复执行一个块，它与有何不同？ while（true）-为什么 while 不起作用，为什么它不起作用？

b) Since loop repeatedly executes a block, how is it any different to while(true) - why doesn't while work, and in what way does it "not work"?

推荐答案

两个函数，循环和反应不纯 loop 通过名称参数进行调用，而 react 进行PartialFunction调用，两者均在原始actor上设置变量。这是因为actor始终没有附加线程。仅当其消息框中有一条消息时，它才会激活。这就是为什么 while（true）会导致100％的CPU使用率并且参与者没有响应的原因。

Both functions, loop and react are not pure. loop takes a call by name parameter and react a PartialFunction, both set variables on the raw actor. This is because an actor does not have a thread attached all the time. It will become active only when there is a message in it's messagebox. This is why a while(true) will lead to 100% cpu usage and the actor not responding.

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