Chapter 4. Having fun with functional data structures

In this chapter you’ll switch gears to begin a fun and interesting part of the Scala language: Scala collections which broadly support two categories of data structures—immutable and mutable.

To understand and benefit from Scala collections, you need to know two concepts: type parameterization and higher-order functions. Type parameterization allows you to create types that take another type as a parameter (similar to Java generics). Higher-order functions let you create functions that take other functions as parameters. These two concepts allow you to create generic and reusable components, like Scala collections.

The Scala collection is one of Scala’s most powerful features. The library implements all the common data structures you need, making it essential for every Scala developer. A recent addition to the collections library is parallel collections. Scala parallel collections allow you to solve data parallelism problems in Scala with ease. You’ll see how the Scala parallel collections library helps when working with large datasets, so buckle up! This will be a fun and exciting ride.

4.1. Introducing type parameterization

4.2. Type variance with covariance and contravariance

4.3. Lower and upper type bounds

4.4. Higher-order functions, including map, flatMap, and friends

4.5. Using foldLeft and foldRight

4.6. Building your own function objects

4.7. Scala collection hierarchy

4.8. Mutable and immutable collections

4.9. Working with List and ListBuffer

4.10. Working with lazy collections: views and streams

4.11. Divide and conquer with parallel collections

4.12. Summary