Book Image

Learn Scala Programming

By : Slava Schmidt
Book Image

Learn Scala Programming

By: Slava Schmidt

Overview of this book

The second version of Scala has undergone multiple changes to support features and library implementations. Scala 2.13, with its main focus on modularizing the standard library and simplifying collections, brings with it a host of updates. Learn Scala Programming addresses both technical and architectural changes to the redesigned standard library and collections, along with covering in-depth type systems and first-level support for functions. You will discover how to leverage implicits as a primary mechanism for building type classes and look at different ways to test Scala code. You will also learn about abstract building blocks used in functional programming, giving you sufficient understanding to pick and use any existing functional programming library out there. In the concluding chapters, you will explore reactive programming by covering the Akka framework and reactive streams. By the end of this book, you will have built microservices and learned to implement them with the Scala and Lagom framework.
Table of Contents (19 chapters)


Semigroup is probably the simplest yet most useful algebraic structure. It is fully defined by two qualities:

  • It is defined for some (possibly infinite) set of elements
  • It has a binary operation defined for any pairs of elements in this set

It also has the following two properties:

  • The operation is closed, which means that the result of the operation belongs to the same set as its operands
  • The operation is associative, meaning that multiple operations should produce the same result, regardless of the order in which they are applied

We can translate these definitions into the Scala code almost literally:

trait Semigroup[S] {
def op(l: S, r: S): S

S denotes the type that the set elements belong to, and op denotes the operation. The result type is also S—we have defined the property of closeness of the operation on the type level. Formally, it is said that S...