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Learn Scala Programming

You're reading from   Learn Scala Programming A comprehensive guide covering functional and reactive programming with Scala 2.13, Akka, and Lagom

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Product type Paperback
Published in Oct 2018
Publisher Packt
ISBN-13 9781788836302
Length 498 pages
Edition 1st Edition
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Author (1):
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Slava Schmidt Slava Schmidt
Author Profile Icon Slava Schmidt
Slava Schmidt
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Table of Contents (19) Chapters Close

Preface 1. An Introduction to Scala 2.13 FREE CHAPTER 2. Understanding Types in Scala 3. Deep Dive into Functions 4. Getting to Know Implicits and Type Classes 5. Property-Based Testing in Scala 6. Exploring Built-In Effects 7. Understanding Algebraic Structures 8. Dealing with Effects 9. Familiarizing Yourself with Basic Monads 10. A Look at Monad Transformers and Free Monad 11. An Introduction to the Akka and Actor Models 12. Building Reactive Applications with Akka Typed 13. Basics of Akka Streams 14. Project 1 - Building Microservices with Scala 15. Project 2 - Building Microservices with Lagom 16. Preparing the Environment and Running Code Samples 17. Assessments 18. Other Books You May Enjoy

Chapter 10

  1. Why does the type of monad transformer reflect the type of the stack "upside-down"?

It is impossible to define a monad composition in general, only in a way specific to the internal effect of the stack. Because of this, the name of the effect is fixed in the name of the transformer and the outer effect becomes a type parameter.

  1. Why is it possible to reuse existing monads for the top layer of the stack?

The return type of the Kleisli arrow fits well with the type of the stack. For this reason, it is possible to produce the result of the proper type by utilizing the flatMap method of the outer monad.

  1. Why is it impossible to reuse existing monads for the bottom layer of the stack?

The argument type of the arrow expects a plain argument. Consequently, we need to extract the effect-free value from the context of internal effect. This is only possible in a...

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