When we're talking about Elixir functions, we can add a special symbol to define default values for our arguments: \\

Example:

defmodule Example do
	def sum(number_one \\ 1, number_two \\ 2) do
		number_one + number_two
	end
end

Example.sum(2, 2)
# 4
Example.sum(5)
# 7
Example.sum()
# 3