Module

Elixir is a functional programming language. Module is used to group functions, like namespace in Clojure.

defmodule Calculator do
  @moduledoc """
  A simple module
  """
  
  @doc """
  Adds two numbers together.
  
  ## Examples
      
      iex> Calculator.add(2, 3)
      5
  """
  def add(a, b) do
    a + b
  end
end

import

Modules can be used in other modules directly like Calculator.add. With import, you can get rid of the prefix.

defmodule MyApp do
  import Calculator

  def sum(a, b, c) do
    # Call add directly instead of Calculator.add
    add(add(a, b), c)
  end
end

Only import specific functions:

defmodule MyApp do
  import Calculator, only: [add: 2]
end

use

use is more powerful.

When use SomeModule is encountered, the __using__/1 macro defined in that module will be called, which can then inject code into the current module.

defmodule Greeter do
  defmacro __using__(opts) do
    quote do
      def hello(name) do
        "Hello, #{name}!"
      end
      
      def greeting_type do
        unquote(opts[:type] || "formal")
      end
    end
  end
end

Use it in another module:

defmodule MyApp do
  use Greeter, type: "casual"
  
  def greet(name) do
    hello(name) <> " Welcome to #{greeting_type()} chat."
  end
end

Module Resolving

When you import or use a module, Elixir doesn't directly look for files - it looks for compiled modules that are available in the current compilation context. Loading paths can be inspected using :code.get_path.

iex -S mix

:code.get_path

Elixir follows a naming convention:

• Module names use PascalCase
• Filenames use snake_case.ex
• Nested modules (like MyApp.User) map to directories (my_app/user.ex)