Using Erlang from Elixir

Elixir code runs in the Erlang VM. The ability to invoke Erlang code from within Elixir allows the use of resources from the entire Erlang ecosystem, and since Elixir code is compiled to the same byte code as Erlang code, there is no performance penalty.

It is also possible to include in an Elixir application the Erlang code that is already compiled.

If you take a closer look, the files we compile in IEx sessions have the .beam extension, and that's exactly the same format Erlang's compiled code gets transformed into.

Getting ready

To use Erlang code in Elixir, we start a new IEx session.

How to do it…

These are some examples of how to invoke Erlang code from Elixir:

  1. Erlang's Application module defines a function named which_applications. This function returns a list of applications being executed in an Erlang VM. This is the way to use this function from Elixir: 
    iex(1)> :application.which_applications

    Note

    The Erlang code would be application:which_applications().

  2. To get information on any Erlang module, there is a function named module_info. To know more about the erlang module, we enter this: 
    iex(2)> :erlang.module_info

    Note

    The Erlang code would be erlang:module_info().

How it works…

In Elixir, Erlang modules are represented as atoms. Functions in these modules are invoked in the same way as any Elixir function.

Note

In Elixir, the atom type is used as an identifier for a given value. In Ruby, the equivalent of the atom is known as the symbol.

There's more…

Existing Erlang libraries can be included in Elixir applications, widening the available options. It is also possible to choose an Erlang implementation of a module over Elixir's.

The Elixir standard library has a List module defined. The Erlang counterpart is lists.

If we wish to get the last element of a list, we could use both modules:

  • We can use Elixir's List module like this: 
    List.last([1,2,3])
  • We can use Erlang's lists module in this manner: 
    :lists.last([1,2,3])

    Note

    The Erlang code for this operation is lists:last([1,2,3]).

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