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

Transforming code


As previously described in this chapter, it's trivial to read and evaluate code in Clojure using the read and eval functions and their variants. Instead of evaluating code right after it is parsed, we can use macros to first transform code programmatically using quoting and unquoting, and then evaluate it. Thus, macros help us define our own constructs that rewrite and transform expressions passed to them. In this section, we will explore the basics of creating and using macros.

Expanding macros

Macros need to be expanded when they are called. All Clojure code is read, macroexpanded, and evaluated by the reader as we described earlier. Let's now take a look at how macroexpansion is performed. As you may have guessed already, this is done using plain Clojure functions.

Interestingly, the reader of the Clojure runtime also uses these functions to process a program's source code. As an example, we will examine how the -> threading macro is macroexpanded. The -> macro can...