Livebook running Erlang instead of Elixir

[aleklisi]

How many changes would it require for the livebook to be able to run Erlang instead of Elixir?

[josevalim]

It is definitely doable, I think it is mostly a matter of replacing the Elixir evaluator by Erlang's evaluator and implementing the editor functionality (code completion, etc).

But getting all of the features, such as the just released smart cells, may be trickier.

[aleklisi]

@josevalim thanks for the reply, but I assume Erlang is also less "livebook friendly" with its variable binding. If you consider Elixir pid = spawn(fn -> receive do _ -> :ok end end) then if you call it over and over again it will work in the same fashion reassigning the new PID to the pid variable while the respective code in Erlang Pid = spawn(fun() -> receive _ -> ok end end) is expected to assign once and then on a second attempt return no match on right-hand-side value.

[jonatanklosko]

@aleklisi actually this particular case shouldn't be a problem. One of the key aspects of Livebook is that the code is evaluated sequentially, there is no global set of variables. So a cell only "sees" the binding from the previous cell. To give an example:

# cell 1
a = ...

# cell 2
b = ...

When cell 2 is evaluated it receives [a: ...] as the current binding and it returns [a: ..., b: ...] as the new binding. When we want to evaluate it again, it receives [a: ...] again and it's all the same.

[CrowdHailer]

This was also discussed here. erlef/gsoc#9

@josevalim apart from being doable, is there any desire to support this feature?
I'm not sure where livebook what's to focus, but in recent conversations the depth of the erlang libraries has been becoming more of a pitch when I've been talking about Elixir. I've recently moved to industrial automation and started using OPCUA which is a giant cumbersome api

[josevalim]

We could certainly support this feature if someone implements it. :) Most of the work is around Monaco (the editor, syntax highlight, intelissense, etc) and most likely some UI changes.