Book Image

Mastering Clojure

By : Akhil Wali
Book Image

Mastering Clojure

By: Akhil Wali

Overview of this book

Clojure is a general-purpose language from the Lisp family with an emphasis on functional programming. It has some interesting concepts and features such as immutability, gradual typing, thread-safe concurrency primitives, and macro-based metaprogramming, which makes it a great choice to create modern, performant, and scalable applications. Mastering Clojure gives you an insight into the nitty-gritty details and more advanced features of the Clojure programming language to create more scalable, maintainable, and elegant applications. You’ll start off by learning the details of sequences, concurrency primitives, and macros. Packed with a lot of examples, you’ll get a walkthrough on orchestrating concurrency and parallelism, which will help you understand Clojure reducers, and we’ll walk through composing transducers so you know about functional composition and process transformation inside out. We also explain how reducers and transducers can be used to handle data in a more performant manner. Later on, we describe how Clojure also supports other programming paradigms such as pure functional programming and logic programming. Furthermore, you’ll level up your skills by taking advantage of Clojure's powerful macro system. Parallel, asynchronous, and reactive programming techniques are also described in detail. Lastly, we’ll show you how to test and troubleshoot your code to speed up your development cycles and allow you to deploy the code faster.
Table of Contents (19 chapters)
Mastering Clojure
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
References
Index

Managing state


A program can be divided into several parts which can execute concurrently. It is often necessary to share data or state among these concurrently running tasks. Thus, we arrive at the notion of having multiple observers for some data. If the data gets modified, we must ensure that the changes are visible to all observers. For example, suppose there are two threads that read data from a common variable. This data gets modified by one thread, and the change must be propagated to the other thread as soon as possible to avoid inconsistencies.

Programming languages that support mutability handle this problem by locking over a monitor, as we demonstrated with the locking form, and maintaining local copies of the data. In such languages, a variable is just a container for data. Whenever a concurrent task accesses a variable that is shared with other tasks, it copies the data from the variable. This is done in order to prevent unwanted overwriting of the variable by other tasks while...