Uncertain about function definition order

Questions / Help
1

Hello!

I am relatively new to Elixir, so far I love it!

I have a little question about pattern matching and function definition order.

I tried to implement a simple factorial function but my editor (vs code with ElixirLS extension) keeps complaining. I tried every order with little success.

function is:

 @spec factorial(non_neg_integer, non_neg_integer) ::
          non_neg_integer | {:error, :invalid_argument}
  def factorial(number, result \\ 1) when is_integer(number) and number > 0,
    do: factorial(number - 1, result * number)

  def factorial(0, result), do: result
  def factorial(invalid_argument, _), do: {:error, :invalid_argument, invalid_argument}

error is:

def factorial/2 has multiple clauses and also declares default values. In such cases, the default values should be defined in a header.
2

Hello and welcome,

This happens because You have result as optional. You can solve this by adding a signature, like this…

def factorial(number, result \\ 1)
def factorial(number, result) when is_integer(number) and number > 0,
    do: factorial(number - 1, result * number)

# etc

and then use result as non optional in the rest.

2 Likes
3

Ho great I understand, thanks a lot @kokolegorille ! :muscle: