Sign In Start Free Trial

Clojure Reactive Programming

By : Leonardo Borges

4.3 (13)

Clojure Reactive Programming

4.3 (13)

By: Leonardo Borges

Overview of this book

If you are a Clojure developer who is interested in using Reactive Programming to build asynchronous and concurrent applications, this book is for you. Knowledge of Clojure and Leiningen is required. Basic understanding of ClojureScript will be helpful for the web chapters, although it is not strictly necessary.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. What is Reactive Programming?

1. What is Reactive Programming?

A taste of Reactive Programming

A bit of history

Signals and events

Implementation challenges

Applications of FRP

Summary

2. A Look at Reactive Extensions

2. A Look at Reactive Extensions

The Observer pattern revisited

Creating Observables

Manipulating Observables

Flatmap and friends

Error handling

Backpressure

Summary

3. Asynchronous Programming and Networking

3. Asynchronous Programming and Networking

Building a stock market monitoring application

Rolling averages

Identifying problems with our current approach

Removing incidental complexity with RxClojure

Summary

4. Introduction to core.async

4. Introduction to core.async

Asynchronous programming and concurrency

core.async

Rewriting the stock market application with core.async

Error handling

Backpressure

Transducers

Summary

5. Creating Your Own CES Framework with core.async

5. Creating Your Own CES Framework with core.async

A minimal CES framework

Exercises

A respondent application

CES versus core.async

Summary

6. Building a Simple ClojureScript Game with Reagi

6. Building a Simple ClojureScript Game with Reagi

Setting up the project

Reagi and other CES frameworks

Summary

7. The UI as a Function

7. The UI as a Function

The problem with complex web UIs

Enter React.js

ClojureScript and Om

Building a simple Contacts application with Om

Intercomponent communication

Exercises

Summary

8. Futures

8. Futures

Clojure futures

Fetching data in parallel

Imminent – a composable futures library for Clojure

The movies example revisited

Futures and blocking IO

Summary

9. A Reactive API to Amazon Web Services

9. A Reactive API to Amazon Web Services

The problem

Infrastructure automation

AWS resources dashboard

CloudFormation

EC2

RDS

Designing the solution

Exercises

Summary

A. The Algebra of Library Design

A. The Algebra of Library Design

The semantics of map

Finding the average of ages

Applicative Functors

Gathering stats about ages

Monads

Summary

B. Bibliography

B. Bibliography

Index

Index

Customer Reviews

4.3 (13)

5 star

76.9%

4 star

0

3 star

7.7%

2 star

7.7%

1 star

7.7%

Finding the average of ages

In this section, we will explore a different use case for the Option Functor. We would like to, given a number of pirates, calculate the average of their ages. This is simple enough to do:

(defn avg [& xs]
  (float (/ (apply + xs) (count xs))))

(let [a (some-> (pirate-by-name "Jack Sparrow") age)
      b (some-> (pirate-by-name "Blackbeard") age)
      c (some-> (pirate-by-name "Hector Barbossa") age)]
  (avg a b c)) ;; 56.666668

Note how we are using some-> here to protect us from nil values. Now, what happens if there is a pirate for which we have no information?

(let [a (some-> (pirate-by-name "Jack Sparrow") age)
      b (some-> (pirate-by-name "Davy Jones") age)
      c (some-> (pirate-by-name "Hector Barbossa") age)]
  (avg a b c)) ;; NullPointerException   clojure.lang.Numbers.ops (Numbers.java:961)

It seems we're back at square one! It's worse now because using...

Search

Your notes and bookmarks