Book Image

Learning Elixir

By : Kenny Ballou, Kenneth Ballou
Book Image

Learning Elixir

By: Kenny Ballou, Kenneth Ballou

Overview of this book

Elixir, based on Erlang’s virtual machine and ecosystem, makes it easier to achieve scalability, concurrency, fault tolerance, and high availability goals that are pursued by developers using any programming language or programming paradigm. Elixir is a modern programming language that utilizes the benefits offered by Erlang VM without really incorporating the complex syntaxes of Erlang. Learning to program using Elixir will teach many things that are very beneficial to programming as a craft, even if at the end of the day, the programmer isn't using Elixir. This book will teach you concepts and principles important to any complex, scalable, and resilient application. Mostly, applications are historically difficult to reason about, but using the concepts in this book, they will become easy and enjoyable. It will teach you the functional programing ropes, to enable them to create better and more scalable applications, and you will explore how Elixir can help you achieve new programming heights. You will also glean a firm understanding of basics of OTP and the available generic, provided functionality for creating resilient complex systems. Furthermore, you will learn the basics of metaprogramming: modifying and extending Elixir to suite your needs.
Table of Contents (16 chapters)
Learning Elixir
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Macro examples


Let's go through some more in-depth examples of using macros to accomplish some pretty cool things, things that are generally fairly difficult to accomplish in other languages.

Debugging and tracing

We'll start with a debugging/tracer module that will enable us to automatically trace the methods of our library.

Note

Of course, this is highly unnecessary since the Erlang VM itself is capable of adding this functionality for us without requiring anything from the developer.

As part of this example, we're going to dive into use and __using__. use as it turns out, is a relatively simple function that invokes the __using__ macro of the module passed. This, in turn, injects the code of the __using__ macro.

For example, let's say we've defined a basic module, UsingTest, as the following code:

defmodule UsingTest do
  defmacro __using__(_opts) do
    quote do
      IO.puts "I'm the __using__/1 of #{unquote(__MODULE__)}"
    end
  end
end

If we then define another, very simple module, say...