Chapter 6

1. What would be the proper effect to represent getting each of the following:

• The first element of some List: Option[?] with None representing an empty list does not have a head element
• A list of tweets: Future[List[Tweet]] as the operation will probably take some time as it goes over the network
• User information from the database for a given userId: Future[Option[?]] with Future denoting the network call and Option denoting no user account for a given userId

2. What is a range of possible values of the following expression: Option(scala.util.Random.nextInt(10)).fold(9)(_-1)

An inclusive [-1;9]

3. What will be the result of the following expression:

Try[Int](throw new OutOfMemoryError()).filter(_ > 10).recover {
  case _: OutOfMemoryError => 100
}(20)

The Try constructor will not catch an OutOfMemoryError, hence the given expression will throw the OutOfMemoryError...