Call by name and laziness in Scala

Call by name is lazy.

  def maybeTwice(b: Boolean, i: => Int) = {
    if(b) 2 * i else 0
  }
  maybeTwice(true, {
    // the block is run
    println("run!")
    3 + 1
  })
  maybeTwice(false, {
    // this block is not run
    println("run!")
    3 + 1
  })