What's the difference between => , ()=>, and Unit=>

Question

I\'m trying to represent a function that takes no arguments and returns no value (I\'m simulating the setTimeout function in JavaScript, if you must know.)

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Answer 1

In the question, you want to simulate SetTimeOut function in JavaScript. Based on previous answers, I write following code:

class Scheduled(time: Int, cb: => Unit) {
  private def runCb = cb
}

object Scheduled {
  def apply(time: Int, cb: => Unit) = {
    val instance = new Scheduled(time, cb)
    Thread.sleep(time*1000)
    instance.runCb
  }
}

In REPL, we can get something like this:

scala> Scheduled(10, println("a")); Scheduled(1, println("b"))
a
b

Our simulation doesn't behave exactly the same as SetTimeOut, because our simulation is blocking function, but SetTimeOut is non-blocking.