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The Clojure Workshop

You're reading from   The Clojure Workshop Use functional programming to build data-centric applications with Clojure and ClojureScript

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Product type Paperback
Published in Jan 2020
Publisher Packt
ISBN-13 9781838825485
Length 800 pages
Edition 1st Edition
Languages
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Authors (5):
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Konrad Szydlo Konrad Szydlo
Author Profile Icon Konrad Szydlo
Konrad Szydlo
Yehonathan Sharvit Yehonathan Sharvit
Author Profile Icon Yehonathan Sharvit
Yehonathan Sharvit
Scott McCaughie Scott McCaughie
Author Profile Icon Scott McCaughie
Scott McCaughie
Thomas Haratyk Thomas Haratyk
Author Profile Icon Thomas Haratyk
Thomas Haratyk
Joseph Fahey Joseph Fahey
Author Profile Icon Joseph Fahey
Joseph Fahey
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Toc

Table of Contents (17) Chapters Close

Preface 1. Hello REPL! 2. Data Types and Immutability FREE CHAPTER 3. Functions in Depth 4. Mapping and Filtering 5. Many to One: Reducing 6. Recursion and Looping 7. Recursion II: Lazy Sequences 8. Namespaces, Libraries and Leiningen 9. Host Platform Interoperability with Java and JavaScript 10. Testing 11. Macros 12. Concurrency 13. Database Interaction and the Application Layer 14. HTTP with Ring 15. The Frontend: A ClojureScript UI Appendix

Multimethods

Clojure offers a way to implement polymorphism with multimethods. Polymorphism is the ability of a unit of code (in our case, functions) to behave differently in different contexts, for example, based on the shape of the data received by the code. In Clojure, we also call it runtime polymorphism because the method to call is determined at runtime rather than at compile time. A multimethod is a combination of a dispatch function and of one or more methods. The two main operators for creating those multimethods are defmulti and defmethod. defmulti declares a multimethod and defines how the method is chosen with the dispatch function. defmethod creates the different implementations that will be chosen by the dispatch function. The dispatch function receives the arguments of the function call and returns a dispatch value. This dispatch value is used to determine which function, defined with defmethod, to invoke. Those are a lot of new terms but don't worry, the following...

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