People seem to use Lisp like it is some impoverished programming model. Why would I want to do things concurrently in one Lisp? Because that's how I use a Lisp system all the time. That's my normal way to do things.

> But you mean a REPL as in a console-style interaction, right?

I mean > 1 REPL as an example how I would use a Lisp concurrently. Yeah, I can switch between REPLs in micro seconds and run > 1 second activities in each of them.

> Any command used in Emacs is an eval step in a REPL

And you can't run simple Lisp code in two commands concurrently, neither in a REPL nor in a command.

> `while-no-input`

Type (while-no-input (dotimes (i 1000000) (print i))) in two Emacs Lisp repls and have them running concurrently.

I understand that GNU Emacs can run external processes, external instances of GNU Emacs, external other Lisp systems, that it can provide some limited form of cooperative threads, ...

I have lived through this stuff 30 years ago and onwards, when many Lisp implementations used cooperative threading (and some had cooperative threads deeply integrated in their Lisp code, other than GNU Emacs in 2024) and over the years switched to native preemptive threading. I also remember when we got Symmetric Multiprocessing in several Lisp systems roughly 15 years ago.