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Learning Elixir

Learning Elixir

By : Kenny Ballou, Kenneth Ballou
5 (1)
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Learning Elixir

Learning Elixir

5 (1)
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 (11 chapters)
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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
1. Introducing Elixir – Thinking Functionally
1. Introducing Elixir – Thinking Functionally
Why functional?
Installing Elixir
Hello, World!
Exercises
Summary
2
2. Elixir Basics – Foundational Steps toward Functional Programming
2. Elixir Basics – Foundational Steps toward Functional Programming
Everything is an expression
A short introduction to types
Invariable variables and pattern matching
Elixir structure
Elixir files
Exercises
Summary
3
3. Modules and Functions – Creating Functional Building Blocks
3. Modules and Functions – Creating Functional Building Blocks
Modules
Anonymous functions
Named functions
Calling functions
Grabbing functions
When patterns aren't enough for matching
Functional algorithms for everyday problems
Mix – the ladle of Elixir
Building functional projects
More to do about modules
Testing with comments
Exercises
Summary
4
4. Collections and Stream Processing
4. Collections and Stream Processing
Keywords, maps, and dictionaries
Flow-based programming
Stream processing and Elixir
Exercises
Summary
5
5. Control Flow – Occasionally You Need to Branch
5. Control Flow – Occasionally You Need to Branch
Branching with Elixir
Examples using branching
Exception handling
Determinism
References
Exercises
Summary
6
6. Concurrent Programming – Using Processes to Conquer Concurrency
6. Concurrent Programming – Using Processes to Conquer Concurrency
Parallel computation and concurrent computation
Erlang processes and OS processes
Basics of Elixir process
Applications
Summary
7
7. OTP – A Poor Name for a Rich Framework
7. OTP – A Poor Name for a Rich Framework
Applications
Gen(eric) behaviours
Supervisors
Exercises
Summary
8
8. Distributed Elixir – Taking Concurrency to the Next Node
8. Distributed Elixir – Taking Concurrency to the Next Node
Obligatory discussion about distributed computing
Another short discussion about networks
Distributed computing with Elixir
Summary
9
9. Metaprogramming – Doing More with Less
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9. Metaprogramming – Doing More with Less
Behaviours and protocols
Abstract syntax trees
Our first macros
Context and macro hygiene
Macro examples
Domain-specific languages
With great power...
Exercises
Summary
Going forward
10
Index
Index

Our first macros

Now that we have the basics of abstract syntax trees, let's dive into macros, the heart of metaprogramming.

Macros, in the context of Elixir, are a means of deferring the evaluation of certain code. That is, instead immediately expanding an expression, say, when a value is passed, the expression will be passed in its quoted form to the macro. The macro would then be able to decide what it should do with the expressions passed.

This may become more clear when comparing macros to functions. For example, let's attempt to (re)create the if-else construct using a function:

defmodule MyIf do

  def if(condition, clauses) do
    do_clause = Keyword.get(clauses, :do, nil)
    else_clause = Keyword.get(clauses, :else, nil)
    case condition do
      val when val in [false, nil] ->
        else_clause
      _ -> do_clause
    end
  end

end

After loading into iex, using MyIf may look something similar to the following lines of code:

iex(1)> c "myif.exs"
[MyIf]
iex(2)> MyIf...
End of Section 2
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