Book Image

Clojure Programming Cookbook

Book Image

Clojure Programming Cookbook

Overview of this book

When it comes to learning and using a new language you need an effective guide to be by your side when things get rough. For Clojure developers, these recipes have everything you need to take on everything this language offers. This book is divided into three high impact sections. The first section gives you an introduction to live programming and best practices. We show you how to interact with your connections by manipulating, transforming, and merging collections. You’ll learn how to work with macros, protocols, multi-methods, and transducers. We’ll also teach you how to work with languages such as Java, and Scala. The next section deals with intermediate-level content and enhances your Clojure skills, here we’ll teach you concurrency programming with Clojure for high performance. We will provide you with advanced best practices, tips on Clojure programming, and show you how to work with Clojure while developing applications. In the final section you will learn how to test, deploy and analyze websocket behavior when your app is deployed in the cloud. Finally, we will take you through DevOps. Developing with Clojure has never been easier with these recipes by your side!
Table of Contents (16 chapters)
Clojure Programming Cookbook
About the Authors
About the Reviewer

Defining multimethods

Defining multimethods is another way to realize polymorphism. The multimethod has a strong dispatch mechanism for polymorphism. Let's see how it works.

Getting ready

You need to add the math.numeric-tower to your project.clj file to run samples (or any other dependency management you are using):

  [[org.clojure/clojure "1.8.0"] 
   [org.clojure/math.numeric-tower "0.0.4"] 

How to do it...

Let's see how to define and use multimethods.

Defining a multimethod

The defmulti creates new multimethods, and the defmethod creates and implements a new method of multimethod associated with a dispatch value.

The following code shows an example of the defmulti of the calculation of the volume of shapes. The first argument is the name of the multimethod and the second argument is the dispatch function:

(defmulti volume :shape) 
;;=> nil 

Now we will define a method for the calculation of cube:

(defmethod volume :cube [shape...