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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.

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:

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.

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.

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.

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.

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.

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.

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.

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.

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

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!