Yejun Su is using Numerical Elixir’s new Livebook project for more than just Numerical Things.

Before Livebook, I write code in IEx, which is a REPL. It has some helpers to ease the way to explore code, but in my opinion, Livebook exceeds in two factors:

Code history
In fact, IEx can enable code history by setting export ERL_AFLAGS="-kernel shell_history enabled" in the shell profile file. You can also search the IEx code history with Ctrl-r and apply it. But as Livebook is essentially a notebook, you can see all texts and evaluation results without the need to set anything.

Visualization
Livebook has a clean UI. You can write documents in Markdown and evaluate Elixir code blocks. It is more continuous, you can review every step of your thought by scrolling the page.