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

Testing with comments


There's another cool feature of the @moduledoc and @doc attributes and that is what's called doctesting. That is, the lines in our comments that look similar to iex sessions can be used as tests where the output return value is the expected result.

Let's return to our flatten project from earlier.

We can add some @doc comments to the function, and add what would look similar to an iex session of us manually testing the function, but in fact, would be tests run by the mix test.

Open the flatten.ex file from earlier and add the @doc attribute:

defmodule Flatten do
  @doc """
  Flatten an arbitrarily nested lists

  ## Examples

      iex> Flatten.flatten [[1, 2], [3], [4, 5]]
      [1, 2, 3, 4, 5]
      iex> Flatten.flatten [1, 2, 3, 4, 5]
      [1, 2, 3, 4, 5]
  """
  def flatten([]), do: []
  def flatten([h|t]) when is_list(h), do: h ++ flatten(t)
  def flatten([h|t]), do: [h] ++ flatten(t)
end

Next, open the flatten_test.exs file as well and add the following line...