Scala Language Type Parameterization (Generics) The Option type
Example
A nice example of a parameterized type is the Option type. It is essentially just the following definition (with several more methods defined on the type):
sealed abstract class Option[+A] {
def isEmpty: Boolean
def get: A
final def fold[B](ifEmpty: => B)(f: A => B): B =
if (isEmpty) ifEmpty else f(this.get)
// lots of methods...
}
case class Some[A](value: A) extends Option[A] {
def isEmpty = false
def get = value
}
case object None extends Option[Nothing] {
def isEmpty = true
def get = throw new NoSuchElementException("None.get")
}
We can also see that this has a parameterized method, fold, which returns something of type B.
