Get Programming with Scala

49 Lazy evaluation

After reading this lesson, you’ll be able to

• Implement functions that use by-name parameters
• Initialize a value lazily by using the keyword lazy

Now that you’ve mastered JSON serialization and deserialization, you’ll learn about lazy evaluation. You already encountered examples of lazy evaluations when discussing Scala collections. For example, the function getOrElse(key: K, default: => V) acting on an instance of type Map[K,V] has two parameters: key, which is eagerly evaluated (or called by value), and default, which is lazily evaluated (or called by name). In this lesson, you’ll see how to evaluate parameters by name (i.e., lazy evaluation), rather than by value (i.e., eager evaluation). You’ll also learn how to initialize ...