The "Hello World" program

In this section, we go through a simple, working Hello World program. We will not go into too much, yet we will provide deeper information in the subsequent sections. For now, we will just define a reactor that waits for one incoming event, prints a message to the standard output once this event arrives, and then terminate.

We start by importing the contents of the io.reactors package:

import io.reactors._ 

This allows us to use the facilities provided by the Reactors framework. In the following snippet, we declare a simple reactor-based program:

object ReactorHelloWorld { 
  def main(args: Array[String]): Unit = { 
    val welcomeReactor = Reactor[String] { self => 
      self.main.events onEvent { name => 
        println(s"Welcome, $name!") 
        self.main.seal() 
      } 
    } 
    val system = ReactorSystem.default("test-system") 
    val ch = system.spawn(welcomeReactor) 
    ch ! "Alan" 
  } 
} 

The program above declares an anonymous reactor called...