When is it better to use Erlang instead of Elixir?

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1

Are there scenarios when it’s better to use Erlang instead of Elixir? If so when and why? Thank you.

2

Sometimes it is simpler to express something in Erlang, at least for me. Also:

  • Erlang can be seamlessly used from Elixir, other way around isn’t always that easy. That is why I created systemd and consulate in Erlang instead of Elixir
  • creating functions with “weird names” is harder in Elixir than in Erlang, so for stuff that needs them, it is easier to write them in Erlang (ex. xmerl modules)
  • Non-macro code generation (AOT, like in Yecc and Leex) is IMHO a little bit easier in Erlang than in Elixir
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3

Interesting question!

Could you elaborate on this? I know that the following works in Elixir:

defmodule Foo do
  name = :"is this weird enough?"
  def unquote(name)(a, b), do: a + b
end

and this technique is not just a ‘weird but useless trick’, it actually sees some real-life usage in places like the testing framework ExUnit, where function names are picked based on strings a user passes to the it and describe macros.

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4

There are few cases when the “weird name” is required:

  • '$handle_undefined_function'/2
  • xmerl uses Tag(Data, Attributes, Parents, E) callbacks in Callback module, so if you have XML tag in form of <foo-bar /> then the function need to be named 'foo-bar'/4

In Erlang it is simple, because any atom can be a function name:

foo() -> ok.

'foo-bar'() -> ok.

'$foo_bar'() -> ok.

'#xml-inheritance#'() -> ok.

In Elixir you need to use unquote/1 to achieve something like that, which can look “unnatural” for many people that do not expect unquote/1 outside of quote/{1,2}.

Another thing is that in Erlang you can do:

M = foo,
F = bar,

M:F().

And in Elixir you need to use apply/3, but that is a minor thing.

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