Understanding Computation

Chapter 1. Just Enough Ruby

The code in this book is written in Ruby, a programming language that was designed to be simple, friendly, and fun. I’ve chosen it because of its clarity and flexibility, but nothing in the book relies on special features of Ruby, so you should be able to translate the code examples into whatever language you prefer—especially another dynamic language like Python or JavaScript—if that helps to make the ideas clearer.

All of the example code is compatible with both Ruby 2.0 and Ruby 1.9. You can find out more about Ruby, and download an official implementation, at the official Ruby website.

Let’s take a quick tour of Ruby’s features. We’ll concentrate on the parts of the language that are used in this book; if you want to learn more, O’Reilly’s The Ruby Programming Language is a good place to start.

Note

If you already know Ruby, you can safely skip to Chapter 2 without missing anything.

Interactive Ruby Shell

One of Ruby’s friendliest features is its interactive console, IRB, which lets us enter pieces of Ruby code and immediately see the results. In this book, we’ll use IRB extensively to interact with the code we’re writing and explore how it works.

You can run IRB on your development machine by typing irb at the command line. IRB shows a >> prompt when it expects you to provide a Ruby expression. After you type an expression and hit Enter, the code gets evaluated, and the result is shown at a => prompt:

$ irb --simple-prompt
>> 1 + 2
=> 3
>> 'hello world' ...