This is a consequence of Elixir (like Erlang) being expression-oriented, not statement oriented. Nearly everything in the language is an expression which evaluates to a value. This is in contrast with statement-oriented languages like C, Java, and others.

This has a few implications:

if and case can be used on the right hand side of = in Elixir, but not in C. Here’s an example:

a = if 1 == 2 do
      "huh"
    else
      "expected"
    end

In C that wouldn’t work since if returns nothing, you’d need to use the ternary expression to achieve a similar result. That choice of term is important. In every language (that I know of) expressions and statements are distinct.

To add on what the others have already said:

Expressions that have “nothing” to return usually return nil or sometimes :ok. An example is for instance if false do ... end (which returns nil because there is no else-block) and IO.puts/1 (which returns :ok).

Then it implicitly returns nil (which is actually a syntactic sugar for the atom :nil, same as true and false are syntactic sugar for :true and :false). Try this:

defmodule Nothing do
  def nothing()
  end
end

And then invoke Nothing.nothing() in iex. You’ll get nil.

Then You call it a method

It’s all about function composition. If it returns nothing, it is most likely a procedure, then it’s not possible to compose with it.

As simple as it is, a function should look like this, and pure function always returns the same output for the same input. You can compose with the powerful |>

Input → Output |> Input → Output |> Input → Output

And coming from Typescript, You will see it’s important to have clear input and output types. Functions are like interfaces.

This video helped me to switch from OOP to FP, because it’s better not to compare with what You already know. In fact, You need to unlearn