[denvaar]

I don't know if it technically qualifies as a REPL[1], but I really enjoy Elixir's interactive console, IEx. What I like about it:

- Tab completion (obviously). Not only for functions/modules/bindings that are in scope, but also when you're in a string and begin typing a path, it will complete the directory names and stuff.

- You can type "h" before a module or function name to read the docs. Similarly, you can do the same with "t" to see type information.

- History of what you've executed, and also a reverse history search feature.

- Not fully "readline compatible", but some basic, standard key bindings work.

- Plenty of handy helper functions.[2]

[1] https://ferd.ca/repl-a-bit-more-and-less-than-that.html

[2] https://hexdocs.pm/iex/1.13/IEx.Helpers.html