Traits

Traits

Traits define interfaces (and can include default implementations). Classes extend them:

trait Greetable {
  def greet: String
}

class Person(name: String) extends Greetable {
  def greet: String = s"Hello, I'm $name"
}

val p = new Person("Alice")
println(p.greet)  // Hello, I'm Alice

Default Implementations

trait Named {
  def name: String
  def shout: String = name.toUpperCase
}

Your Task

Define a trait Shape with an abstract method area: Double. Then define a class Circle(radius: Double) extends Shape that implements area as 3.14159 * radius * radius.