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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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10
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...

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