Professional Scala: Combine object-oriented and functional programming to build high-performance applications by Mads Hartmann & Ruslan Shevchenko

Author:Mads Hartmann & Ruslan Shevchenko [Hartmann, Mads]
Language: eng
Format: epub
Publisher: Packt Publishing
Published: 2018-07-30T23:00:00+00:00

Chapter 5. Scala Type System

In the previous chapter, we covered how to work with lists, which made us familiar with some design principles of the whole collections library. We also covered how to generalize to sequences and covered some more relevant data structures. Finally, we also covered how collections relate to monads and how we can use that knowledge to use some powerful abstractions in our code.

In this chapter, we will cover the type system and polymorphism. We will also cover the different types of variance, which provides a way to constrain parameterized types. Finally, we will cover some advanced types such as abstract type members, option, and so on.

Scala is statically typed. This means that the type of variables are known at compile time. The main advantage of statically typed languages is that a lot of checks can be done by the compiler, thus increasing the number of trivial bugs that are caught at an early stage. Statically typed languages are also friendlier to refactoring, as the programmer can feel safer about their changes as long as the code compiles.

However, Scala is more than statically typed. In this chapter, we will see how Scala's expressive type system enables and enforces statically typed sound abstractions. The ability to infer types reduces the programmers' workload of annotating the program with redundant type information. This chapter will build upon the fundamentals required for the next chapter, where will be talking about type classes and a type of polymorphism they enable: ad hoc polymorphism.

By the end of this chapter, you will be able to:

Identify the Scala type hierarchy

Use the features the Scala type system provides

Identify abstractions that the Scala type system enables

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