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)


A group adds an invertibility property to the properties of the monoid, which means that for every element, a, from the set, S, on which the group is defined, there is an inverse element so that the result of the operation on both of them is an identity element.

Formalized in the code, it looks like the following:

trait Group[S] extends Monoid[S] {
def inverse(a: S): S

The ScalaCheck property for this new law looks similar to the properties we defined for semigroup and monoid:

def invertibility[S : Group : Arbitrary]: Prop =
forAll((a: S) => {
val m = implicitly[Group[S]]
m.op(a, m.inverse(a)) == m.identity && m.op(m.inverse(a), a) == m.identity

Like we did previously, we can define an overarching check that aggregates single properties:

def groupProp[S : Group: Arbitrary]: Prop = monoidProp[S] && invertibility[S]

By adding a commutative property...