Free Elixir course. Sign Up for tracking progress →

Elixir: Modules

In Elixir, functions are grouped by modules that play the role of namespaces. For example, in the previous exercise we used the function puts(text) from module IO:

IO.puts("Hello, World!")

Modules are defined with a special contstruct defmodule/do/end:

# use CamelCase for name
defmodule HexletBasics do
  # Here goes module contains

Elixir allows the creation of multiple modules in the same file, but there is a convention to have only one module per file with the same name as the module but in snake_case.

Modules can be nested. By convention, we create nested modules when they are located in a directory. For example, there's the module HexletBasics.Application located in lib/hexlet_basics/application.ex directory.

defmodule HexletBasics.Application do
  # Function
  def hello do
    IO.puts("Hello, World!")

Function calls for nested modules are the same as for flat modules. First, we put the module's full name, then a function call.


There is a special module Kernel which functions we can call directly.

is_number(13) # true

Kernel contains basic language primitives for arithmetic operations, spawning processes, data type handling, macros for defining new functionality, and more.


Create module My.Super.Module and put the function hello() we defined above

The exercise doesn't pass checking. What to do? 😶

If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:

  • Be sure to attach the test output, without it it's almost impossible to figure out what went wrong, even if you show your code. It's complicated for developers to execute code in their heads, but having a mistake before their eyes most probably will be helpful.
In my environment the code works, but not here 🤨

Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.

My code is different from the teacher's one 🤔

It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.

In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.

I've read the lessons but nothing is clear 🙄

It's hard to make educational materials that will suit everyone. We do our best but there is always something to improve. If you see a material that is not clear to you, describe the problem in “Discussions”. It will be great if you'll write unclear points in the question form. Usually, we need a few days for corrections.

By the way, you can participate in courses improvement. There is a link below to the lessons course code which you can edit right in your browser.


If you got stuck and don't know what to do, you can ask a question in our huge and friendly community