Toy Robot - The Elixir Version
Toy Robot - The Elixir Version
About the Book
The Toy Robot exercise was originally developed by Jon Eaves. He explains why he did it in this blog post.
If you're a new Elixir developer who's gone through some basic Elixir tutorials and you're looking for the next thing to build your skills, this book is a great start. It covers the Toy Robot exercise from start to finish, testing with Elixir features such as ExUnit and Doctests along the way.
The Toy Robot exercise is commonly used in interviews as the ways to solve it in any language are not as simple as they first may seem. This book covers one implementation of this exercise in Elixir. It is not intended to be the most perfect implementation of the Toy Robot exercise possible, but instead is my personal take on it.
In this book, I demonstrate best practices for developing a small Mix application that can solve the Toy Robot exercise. Along the way, you'll learn about:
- How to break a complex problem down into small, approachable chunks
- When to use Doctests or regular ExUnit tests
- Tradeoffs between different ways of pattern matching
- How to work with Elixir processes using GenServer + DynamicSupervisor
The Toy What Now?
The Toy Robot! It's a very common interview exercise given to new programmers. Here's the variant of the problem's description that we use in the book:
The application is a simulation of a toy robot moving on a square tabletop, of dimensions 5 units x 5 units. There are no other obstructions on the table surface. The robot is free to roam around the surface of the table. Any movement that would result in the robot falling from the table is prevented, however further valid movement commands are still allowed.
The application reads a file using a name passed in the command line, the following commands are valid:
- PLACE X,Y,F
Here's some rules for these commands:
- PLACE will put the toy robot on the table in position X,Y and facing NORTH, SOUTH, EAST or WEST.
- The origin (0,0) is the SOUTH WEST most corner.
- All commands are ignored until a valid PLACE is made.
- MOVE will move the toy robot one unit forward in the direction it is currently facing.
- LEFT and RIGHT rotates the robot 90 degrees in the specified direction without changing the position of the robot.
- REPORT announces the X,Y and F of the robot.
The file is assumed to have ASCII encoding. It is assumed that the PLACE command has only one space, that is PLACE 1, 2, NORTH is an invalid command. All commands must be in upcase, all lower and mixed case commands will be ignored.
All of that may seem a little bit overwhelming but if you break it down into little chunks and tackle those chunks one-at-a-time (like this book does!) it becomes much easier.
1. Introducing the Toy Robot
- Simplifying the problem
- Creating the application
- The MOVE command
- Moving west
- Moving north and south
- Moving in the right direction
- Turn left!
- Turn right!
2. Catching bugs
- Finding the bugs within
- Regression testing the turn_right function
- Regression testing the move function
- Regression testing the move_west function
- Regression testing the move_north and move_south functions
- Jumping back to the manual test
3. Placing the robot on a table
- The Table module
- The missing link
4. Building our simulation
- Moving a robot, within a simulation
- Turning a robot, within a simulation
- Reporting the robot’s position
5. Reading and handling commands
- The Command Interpreter
- The Command Runner
- Piecing it all together
6. Building the CLI
- Reading commands from a file
- Verifying the robot’s behaviour
I The Toy Robot Game
7. A Single, Supervised Player
- A single player
- Let it crash!
- Watching processes with supervisors
- Giving names to players
8. Multiplayer Toy Robot
Prelude: a short refactor involving
- Creating a Game
- Handling an invalid placement (off the board)
- Handling an invalid placement (square occupied)
- A refactoring interlude: Breaking Server apart
- Preventing robots from colliding
- Preventing robots from respawning in occupied spaces
- The End
- Prelude: a short refactor involving
- 7. A Single, Supervised Player
The Leanpub 45-day 100% Happiness Guarantee
Within 45 days of purchase you can get a 100% refund on any Leanpub purchase, in two clicks.
See full terms
Free Updates. DRM Free.
If you buy a Leanpub book, you get free updates for as long as the author updates the book! Many authors use Leanpub to publish their books in-progress, while they are writing them. All readers get free updates, regardless of when they bought the book or how much they paid (including free).
Most Leanpub books are available in PDF (for computers), EPUB (for phones and tablets) and MOBI (for Kindle). The formats that a book includes are shown at the top right corner of this page.
Finally, Leanpub books don't have any DRM copy-protection nonsense, so you can easily read them on any supported device.
Ansible for KubernetesJeff Geerling
Ansible is a powerful infrastructure automation tool. Kubernetes is a powerful application deployment platform. Learn how to use these tools to automate massively-scalable, highly-available infrastructure.
Practical FP in Scala: A hands-on approachGabriel Volpe
A practical book aimed for those familiar with functional programming in Scala who are yet not confident about architecting an application from scratch.
Together, we will develop a purely functional application using the best libraries in the Cats ecosystem, while learning about design patterns and best practices.
Functional Design and ArchitectureAlexander Granin
Software Design in Functional Programming, Design Patterns and Practices, Methodologies and Application Architectures. How to build real software in Haskell with less efforts and low risks. The first complete source of knowledge.
Production HaskellMatt Parsons
Are you excited about Haskell, but don't know where to begin? Are you thrilled by the technical advantages, but worried about the unknown pitfalls? This book has you covered.
Tame your Work FlowSteve Tendon and Daniel Doiron
Do you need a high performance enterprise governance approach improving management, execution and delivery while dealing with multiple projects/products, events, stakeholders and teams? Giving you better bottom line results, faster time to market, less work, better predictability, happier employees, and delighted clients? Then learn about TameFlow!
Ansible for DevOpsJeff Geerling
Ansible is a simple, but powerful, server and configuration management tool. Learn to use Ansible effectively, whether you manage one server—or thousands.
Machine Learning EngineeringAndriy Burkov
"If you intend to use machine learning to solve business problems at scale, I'm delighted you got your hands on this book."
—Cassie Kozyrkov, Chief Decision Scientist at Google
"Foundational work about the reality of building machine learning models in production."
—Karolis Urbonas, Head of Machine Learning and Science at Amazon
C++ Best PracticesJason Turner
Level up your C++, get the tools working for you, eliminate common problems, and move on to more exciting things!
Composing SoftwareEric Elliott
All software design is composition: the act of breaking complex problems down into smaller problems and composing those solutions. Most developers have a limited understanding of compositional techniques. It's time for that to change.
El Manual del ManagerKeyvan Akbary, Félix López, and Álvaro Salazar
¿Has deseado alguna vez el haber tenido una buena introducción al rol del Engineering Manager? En este libro aprenderás lo necesario para ejercer el rol de una manera efectiva: Expectativas y Responsabilidades del Rol, 1-1s, Ayudar a Crecer, Objetivos, Planes de Carrera, Cultura, Feedback, Contratación, Cultura de Producto y mucho más.
The Tester's Library
8 BooksThe Tester's Library consists of eight five-star books that every software tester should read and re-read. As bound books, this collection would cost over $200. Even as e-books, their price would exceed $80, but in this bundle, their cost is only $49.99. Here are the books, and why they should be in your library: Perfect Software and Other...
11 BooksIn this bundle, you will find 10 different agile books. They are about different aspects of being agile. - finding a job - doing coding dojo's - Retrospectives - Personal kanban - a non-typical coaching book and even a book that gives you an insight in the lives of some agile people.
WTFlop 6M + HU - Beta Bundle
Marionette.js A to Z
Build A Better Backbone App
3 BooksThe best way to learn new development skills is through experience, but that takes time you don't have.Get the best of both worlds with this bundle: you'll learn how to produce modern web applications by learning from experienced developers like Derick Bailey and David Sulc. BackboneJS is one of the favorite tools on the web today, but it...
General Systems Thinker Bundle
5 BooksThe General Systems Thinker Bundle is just that: a bundle of five books to advance the reader one giant step toward improved thinking, based on General Systems principles. Four of the books are the complete General Systems Series. The fifth is fictional piece which shows some general systems thinkers in action. It's a mystery in which a group of...
Experiential Learning Bundle
4 BooksThis bundle provides all four volumes of the popular Experiential Learning Series at a savings of $20 over the price if purchased separately.
2 BooksAfter getting up and running with Ansible in Jeff Geerling's Ansible for DevOps, strengthen your skills managing tens to thousands of instances and services in Amazon's AWS cloud with Yan Kurniawan's Ansible for AWS.
Learn ECMAScript 6 inside and out
2 BooksFor any technology, it helps to get multiple points of view on the functionality to get the best possible understanding. For ECMAScript 6/2015, no two resources are recommended more frequently thanExploring ES6by Dr. Axel Rauschmayer andUnderstanding ECMAScript 6by Nicholas C. Zakas. These two points of view, investigating the specification and...
Software architecture, for systems old and new
2 BooksThis bundle includes books about hands-on software architecture.