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Understanding Call-By-Name in Scala

I am new to scala language, therefore I will be grateful if someone could explain me this code-snippet :

object C  {

  def main(args: Array[String]) = {
    measure("Scala"){
      println("Hello Back")
    }
  }

  def measure(x: String)(y: => Unit){
   println("Hello World " + x)
  }
}

Console output :

Hello World Scala

My question is why the program didn't print Hello Back as well? Also is the function/object ;whose body is the instruction println("Hello Back"); stored somewhere on the heap?

Solution 
  • {
      println("Hello Back")
}

    this is a code block, equal to:

    def f = {println("Hello World")}
measure("Scala")(f)

    so for measure method, you need to explicitly call:

      def measure(x: String)(y: => Unit){
   println("Hello World " + x)
   y
  }