Scala Programming Projects

Composing transformations with for... yield

Using the same db: Map[String, Int] phrase, containing the ages of different people, the following code is a naive implementation of a function that returns the average age of two people:

def averageAgeA(name1: String, name2: String, db: Map[String, Int]): Option[Double] = {  val optOptAvg: Option[Option[Double]] =    db.get(name1).map(age1 =>      db.get(name2).map(age2 =>        (age1 + age2).toDouble / 2))  optOptAvg.flatten}val db = Map("John" -> 25, "Rob" -> 40)averageAge("John", "Rob", db)// res6: Option[Double] = Some(32.5)averageAge("John", "Michael", db)// res7: Option[Double] = None

The function returns Option[Double]. If name1 or name2 cannot be found in the db map, averageAge returns None. If both names ...