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Programming Kotlin

You're reading from   Programming Kotlin Get to grips quickly with the best Java alternative

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Product type Paperback
Published in Jan 2017
Publisher Packt
ISBN-13 9781787126367
Length 420 pages
Edition 1st Edition
Languages
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Authors (2):
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Stefan Bocutiu Stefan Bocutiu
Author Profile Icon Stefan Bocutiu
Stefan Bocutiu
Stephen Samuel Stephen Samuel
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Stephen Samuel
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Toc

Table of Contents (14) Chapters Close

Preface 1. Getting Started with Kotlin FREE CHAPTER 2. Kotlin Basics 3. Object-Oriented Programming in Kotlin 4. Functions in Kotlin 5. Higher Order Functions and Functional Programming 6. Properties 7. Null Safety, Reflection, and Annotations 8. Generics 9. Data Classes 10. Collections 11. Testing in Kotlin 12. Microservices with Kotlin 13. Concurrency

Pure functions


In functional programming, the concept of a pure function is one that holds the following two properties:

  • The function should always return the same output for the same input

  • The function should not create any side effects

The first property means that when a function is invoked, the value returned should always be the same whenever the same input is used. A simple example is abs. The absolute value of an integer is always the same for the same input. A pure function can depend only on the input, but it does not have to necessarily use all the input types.

The second property is that a function should not cause any observable changes outside the function. So the function cannot depend on any external mutable state, change variables that exist outside the function, or write I/O.

If a function is said to be pure, then the function can be replaced at the call site with the result of the expression. Going back to the absolute function, any code that depends on abs(-4) can be replaced...

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