Elixir Tips

This article is all about saying that Elixir 1.6.3 supports comments in middle of |> , when, | still you do mix format .

a. Comments in the middle of pipelines

I assume that you are in the Elixir version of <1.6.3

Create a file comment.ex and add the following code inside the file

defmodule Comment do
  def square(number), do: number * number
  def cube(number), do: number * number * number


  def run(number) do
    number
    # this is square function
    |> square
    # this is cube function
    |> cube
    # this is used for inspecting the results
    |> IO.inspect()
  end
end

After adding the content to the file run the following command

$ mix format comment.ex

I hope that you are in the same directory of the file comment.ex . The formater converts the above code into the following format.

defmodule Comment do
  def square(number), do: number * number
  def cube(number), do: number * number * number

  def run(number) do
    # this is square function
    # this is cube function
    # this is used for inspecting the results
    number
    |> square
    |> cube
    |> IO.inspect()
  end
end

Did you observe that all the comments are moved to top of definition. But this is updated in Elixir v1.6.3 . The comments are placed in the middle of pipelines in the Elixir v1.6.3

Now install Elixir V1.6.3 and try again. It still supports that comments in the middle of pipelines.

b. comments in the middle of | expressions

@spec square integer()::
                    :ok
                    | :invalid
                    # :unknown
                    | :other

c. comments in the middle of when

Similarly, we can comment in the middle of when guards like in the following

Here, inside the file, I added another function or_gate_truth/2 for showing the demo.

#comment.ex

defmodule Comment do  

  ...  

def or_gate_truth(x, y)
    #checking x is 1
    when x == 1
    #checking y is 1
    when y ==1 do
    True
  end

end

However, if you format the file mix format comment.ex , the formatter still collects all the comments to top of the function like in the following way in ELixir < 1.6.3

defmodule Comment do
  ...  

  # checking x is 1
  # cheking y is 1
  def or_gate_truth(x, y)
      when x == 1
      when y == 1 do
    True
  end
end