Book Image

Clojure High Performance Programming

By : Shantanu Kumar
Book Image

Clojure High Performance Programming

By: Shantanu Kumar

Overview of this book

<p>Clojure is a young, dynamic, functional programming language that runs on the Java Virtual Machine. It is built with performance, pragmatism, and simplicity in mind. Like most general purpose languages, Clojure’s features have different performance characteristics that one should know in order to write high performance code.<br /><br />Clojure High Performance Programming is a practical, to-the-point guide that shows you how to evaluate the performance implications of different Clojure abstractions, learn about their underpinnings, and apply the right approach for optimum performance in real-world programs.<br /><br />This book discusses the Clojure language in the light of performance factors that you can exploit in your own code.</p> <p>You will also learn about hardware and JVM internals that also impact Clojure’s performance. Key features include performance vocabulary, performance analysis, optimization techniques, and how to apply these to your programs. You will also find detailed information on Clojure's concurrency, state-management, and parallelization primitives.</p> <p>This book is your key to writing high performance Clojure code using the right abstraction, in the right place, using the right technique.</p>
Table of Contents (15 chapters)
Clojure High Performance Programming
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Validating and watching the reference types


Vars (both static and dynamic), atoms, refs, and agents provide a way to validate the value being set as state—a validator function that accepts a new value as argument and returns a logical true on success, or throws exception/returns a logical false (false and nil values) on error. They all honor what the validator function returns. On success, the update goes through and on encountering an error, an exception is thrown instead. The following is the syntax of how validators can be declared and associated with the reference types:

(def t (atom 1 :validator pos?))
(def g (agent 1 :validator pos?))
(def r (ref 1 :validator pos?))
(swap! t inc) ; ; goes through, value after increment (2) is positive
(swap! t (constantly -3))  ; throws exception
(def v 10)
(set-validator! (var v) pos?)
(set-validator! t #(>= % 10))
(set-validator! g #(>= % 10))
(set-validator! r #(>= % 10))

Validators cause actual failure within a reference type while updating...