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Elixir & Phoenix: Scalable Backend Development · Lesson

Functions, Modules, and Pipelining

Learn to define functions, organize code into modules, and use the pipe operator for clear data transformations.

Functions, Modules, and Pipelining is a free Elixir & Phoenix: Scalable Backend Development lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Elixir & Phoenix: Scalable Backend Development learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Introduction to Elixir Functions

In Elixir, functions are the building blocks of your programs. They take inputs, perform operations, and return outputs.

Elixir functions are designed to be pure: they don't change data outside their scope and always produce the same output for the same input. This makes your code predictable and easier to reason about.

Defining Public Functions

You define public functions using the def keyword. These functions can be called from anywhere within your application, provided they are part of a module.

Let's create a simple function that adds two numbers:

defmodule MathOperations do
  def add(a, b) do
    a + b
  end
end

IO.puts "Sum of 5 and 3: #{MathOperations.add(5, 3)}"

Defining Private Functions

Sometimes you need helper functions that should only be used internally within a module. For these, you use the defp keyword.

Private functions cannot be called directly from outside their defining module. This helps encapsulate logic.

defmodule SecretOperations do
  defp secret_add(a, b) do
    a + b + 10 # A 'secret' addition
  end

  def public_operation(x, y) do
    secret_add(x, y)
  end
end

IO.puts "Result of public operation: #{SecretOperations.public_operation(2, 3)}"
# SecretOperations.secret_add(1, 2) would cause an error if called directly outside the module.

Function Arity and Clauses

Arity refers to the number of arguments a function takes. Elixir allows you to define multiple function clauses with the same name but different arities or different patterns for arguments.

This enables powerful pattern matching (covered in a previous lesson) to handle different scenarios cleanly within a single function definition.

defmodule Greeter do
  def greet("Alice"), do: "Hello, Alice!"
  def greet(name), do: "Hi there, #{name}!"
end

IO.puts Greeter.greet("Alice")
IO.puts Greeter.greet("Bob")

Anonymous Functions

Anonymous functions (also called lambdas) are functions without a name. They are often used when you need to pass a function as an argument to another function, or for short, one-off operations.

You define them using the fn keyword.

adder = fn a, b -> a + b end
multiplier = fn x, y -> x * y end

IO.puts "Anonymous add: #{adder.(10, 20)}"
IO.puts "Anonymous multiply: #{multiplier.(4, 5)}"

Organizing Code with Modules

Modules in Elixir are containers for organizing related functions and data. They help prevent naming conflicts and make your code more structured and maintainable.

You define a module using the defmodule keyword. It's common practice for module names to start with an uppercase letter, following Elixir's naming conventions.

Creating Your First Module

Let's put our add function inside a module called Calculator. This makes it clear that the add function is part of a set of calculator-related operations.

defmodule Calculator do
  def add(a, b) do
    a + b
  end

  def subtract(a, b) do
    a - b
  end
end

IO.puts "Module defined!"

Calling Module Functions

To call a function defined within a module, you use the module's name, followed by a dot (.), and then the function name with its arguments.

This explicit naming helps you understand where a function comes from.

defmodule Calculator do
  def add(a, b), do: a + b
  def subtract(a, b), do: a - b
end

IO.puts "10 + 5 = #{Calculator.add(10, 5)}"
IO.puts "10 - 5 = #{Calculator.subtract(10, 5)}"

Introducing the Pipe Operator `|>`

The pipe operator |> is one of Elixir's most beloved features. It makes sequences of function calls incredibly readable, flowing data from one function to the next.

Think of it as taking the result of the expression on the left and passing it as the first argument to the function call on the right.

Pipelining in Action

Instead of nesting function calls like function_c(function_b(function_a(data))), the pipe operator lets you write it as data |> function_a() |> function_b() |> function_c().

This reads like a series of steps, making complex data transformations much clearer.

defmodule DataProcessor do
  def double(x), do: x * 2
  def add_five(x), do: x + 5
  def to_string(x), do: to_string(x)
end

result = 10 
         |> DataProcessor.double() 
         |> DataProcessor.add_five() 
         |> DataProcessor.to_string()

IO.puts "Processed result: #{result}"

Check Your Understanding

Which of the following statements about Elixir functions, modules, and the pipe operator are true?

Recap: Functions, Modules & Pipes

Great job! In this lesson, you learned the essentials of organizing and transforming data in Elixir:

  • How to define public (`def`) and private (`defp`) functions.
  • The importance of modules (`defmodule`) for structuring your code.
  • How the pipe operator (`|>`) dramatically improves readability for sequential data transformations.

These concepts are fundamental to writing clear, maintainable, and functional Elixir applications. Keep practicing!

Frequently asked questions

Is the “Functions, Modules, and Pipelining” lesson free?

Yes — the full text of “Functions, Modules, and Pipelining” is free to read here on the web, and the Elixir & Phoenix: Scalable Backend Development course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Elixir & Phoenix: Scalable Backend Development course, upgrade to CoddyKit PRO.

What will I learn in “Functions, Modules, and Pipelining”?

Learn to define functions, organize code into modules, and use the pipe operator for clear data transformations. You practise Elixir & Phoenix: Scalable Backend Development with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Elixir & Phoenix: Scalable Backend Development?

No prior experience is required. Elixir & Phoenix: Scalable Backend Development on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Functions, Modules, and Pipelining” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Elixir & Phoenix: Scalable Backend Development lesson?

Yes. Every Elixir & Phoenix: Scalable Backend Development lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Functions, Modules, and Pipelining
  2. Working with Enumerable Collections
  3. Recursion and Higher-Order Functions
  4. Lazy Evaluation with the Stream Module
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