Using Elixir module from Erlang fails

Question

I am trying to use in Erlang module a beam-file compiled from Elixir source. It raises error when I run Erlang node but I can use the code directly from Elixir.

Elixir module:

defmodule Recursion do
  def print_multiple_times(msg, n) when n <= 1 do
    IO.puts msg
  end

  def print_multiple_times(msg, n) do
    IO.puts msg
    print_multiple_times(msg, n - 1)
  end
end

Erlang module:

-module(use_recur).
-define(elixir__recursion, 'Elixir.Recursion').

-export([hey/0]).

hey() ->
    ?elixir__recursion:print_multiple_times("Hello!", 3).

Compile both:

$ rm -f *.beam $ elixirc recursion.ex
$ erlc use_recur.erl

Run Erlang:

$ erl -run use_recur hey -run init stop -noshell {"init terminating in do_boot",{undef,[{'Elixir.IO',puts,["Hello!"],[]},{'Elixir.Recursion',print_multiple_times,2,[{file,"recursion.ex"},{line,7}]},{init,start_em,1,[]},{init,do_boot,3,[]}]}} init terminating in do_boot ({undef,[{Elixir.IO,puts,Hello!,[]},{Elixir.Recursion,print_multiple_times,2,[{},{}]},{init,start_em,1,[]},{init,do_boot,3,[]}]})

Crash dump is being written to: erl_crash.dump...done

Elixir script:

Recursion.print_multiple_times "Hello!", 3

Runs successfully:

$ elixir elx_recur.exs  
Hello!
Hello!
Hello!

Why does it happen? I'd say Erlang's output should be the same.

You probably need to add the directory containing beam files for Elixir to erl using -pa (e.g. erl -pa /path/to/elixir/ebin ...). The error means Erlang could not find the 'Elixir.IO' module. — Dogbert
– Dogbert, Commented Jul 9, 2017 at 21:07
Alexanders-MacBook-Air:~ alexander$ erl -pa /usr/local/Cellar/elixir/1.4.5/lib/elixir/ebin -run use_recur hey -run init stop -noshell Hello! Hello! Hello! Alexanders-MacBook-Air:~ alexander$ ls /usr/local/Cellar/elixir/1.4.5/lib/elixir/ebin/ | grep Elixir.String.beam Elixir.String.beam — peroksid
– peroksid, Commented Jul 9, 2017 at 21:15

Dogbert · Accepted Answer · 2017-07-09 21:37:15Z

3

The error means that Erlang could not find a module named 'Elixir.IO'. This module is part of core Elixir. You'll need to add the ebin folder of your Elixir installation to Erlang's load path using -pa (or other similar flags like -pz) to make Erlang load Elixir's core libraries, as that folder contains the compiled .beam files of Elixir core, including Elixir.IO.beam.

erl -pa /path/to/elixir/ebin ...

answered Jul 9, 2017 at 21:37

Dogbert

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