Did you know that IO.inspect/2 returns the the first argument and accepts a label option as a second argument. This makes it a perfect tool to logging intermediate results in a pipeline, as well as intermediate results in a function. Take the following pipeline, for example:

def get_gifts(santa, wishlist, snack) do
  santa
  |> receives_wishlist(wishlist)
  |> leaves_presents
  |> eats(snack)
  |> wakeup_to
end

Now lets say that you don’t get your gifts. Try the following:

def get_gifts(santa, wishlist, snack) do
  santa
  |> receives_wishlist(wishlist)
  |> IO.inspect(label: "after wishlist received")
  |> leaves_presents()
  |> IO.inspect(label: "after presents")
  |> eats(snack)
  |> wakeup_to()
  |> IO.inspect(label: "result")
end