[tarboreus]

You write it in the editor and send statements to the REPL. You're not just sitting looking at a command line. The REPL is a conversation with running state, but the conversation doesn't have to take place only through a single blinking terminal window. In proper REPL-driven development, the editor is fully integrated with the running session, and you can evaluate either in an attached terminal session or through your editor. Or by attaching whatever other tools to the running session.

[mikelevins]

Yes, exactly. It's perhaps my fault for not making this more explicit in the essay, but the "repl" in "repl-driven programming" does not mean the repl window.

[O_H_E]

Yeah, I suggest you expand upon that, or perhaps another article showing that "conversation". Unfortunately, some people - including me - have only used a repl in "one-direction" and have to copy stuff back and forth.

[mikelevins]

That's a good suggestion. Walking through a set of interactions is a solid idea.

For what it's worth, there are some videos around of people actually doing it with Lisp and Smalltalk systems, and pjmlp already posted a pile of them elsewhere in this thread.

I can add a few more:

Kalman Reti walking through some interactions with a Symbolics LispM repl:

https://www.youtube.com/watch?v=o4-YnLpLgtk

Brian Mastenbrook demonstrating Interlisp's SEDIT structure editor in the Xerox Lisp environment:

https://www.youtube.com/watch?v=2qsmF8HHskg

Rainer Joswig (lispm here on HN) showing us a little bit of repl and Zmacs interaction on a Symbolics Lisp Machine:

https://www.youtube.com/watch?v=LIGt5OwkoMA&list=PLN1hNlVqKB...

Rainer again, showing some simple interactions with Macintosh Common Lisp, which was my daily driver for years:

https://www.youtube.com/watch?v=GKG8cJl70mo

Ruby programmer Avdi Grimm shows some things that he found cool about Pharo Smalltalk:

https://www.youtube.com/watch?v=HOuZyOKa91o

Dan Ingalls (one of the original authors of Smalltalk) in a 2017 demo of Smalltalk 76:

https://www.youtube.com/watch?v=NqKyHEJe9_w

There are some other things I'd like to find for lists like this, but haven't been able to. In particular, a good demo of Apple's SK8 would be great.

If you can imagine a full-color Hypercard that could crack open and reprogram absolutely everything on the screen, including the machine code that drew the window system's widgets, all in a repl while the code was live; in which you could grab an arbitrary widget and drop it on the repl window to get a live variable reference to the widget, and then inspect it, operate on it, and reprogram it, again, while everything continued to run; in which you could build new window-system widgets by snapping together shapes and telling them to become widgets; in which you were not limited to HyperTalk for coding and text strings for data, but had a full Common Lisp at your disposal plus a Minsky-style frame system for representing data and knowledge, then you have some idea of what SK8 was like.