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

Reading and evaluating code


Let's have a look at how code can be parsed and evaluated in Clojure. The most elementary way to convert text into an expression is by using the read function. This function accepts a java.io.PushbackReader instance as its first argument, as shown here:

user> (read (-> "(list 1 2 3)"
                .toCharArray
                java.io.CharArrayReader.
                java.io.PushbackReader.))
(list 1 2 3)

Note

These examples can be found in src/m_clj/c4/read_and_eval.clj of the book's source code.

In this example, a string containing a valid expression is first converted into an instance of java.io.PushbackReader and then passed to the read function. It seems like a lot of unnecessary work to read a string, but it is due to the fact that the read function deals with streams and readers, and not strings. If no arguments are passed to the read function, it will create a reader from the standard input and prompt the user to enter an expression to be parsed. The...