(shameless plug alert)

This is how my WIP (verrrry WIP) game engine written in Guile Scheme works. It is built explicitly to enable iterative, live development.

2 year old video of a precursor to the current project: https://dthompson.us/functional-reactive-programming-in-sche...

Simple example program: https://git.dthompson.us/sly.git/blob/HEAD:/examples/simple....

More complicated minesweeper example: https://git.dthompson.us/sly.git/blob/HEAD:/examples/mines/m...

Home page: https://dthompson.us/pages/software/sly.html

Hoping to get a 0.2 release out the door in time for the Lisp Game Jam coming up in April.

You can do that right now with Love2D and a stub game loop that sources the actual implementations every second or two.

That is a far cry from a REPL.

It's better than a REPL, that allows you to write a game completely live. I'm not sure what you think is lost since you didn't back up what you are saying with anything.

It is strictly less powerful than a REPL. Claiming that you can't live code a game at a REPL is false, because I do it on a regular basis. When I write games in Scheme, I use a REPL to write the game live, doing all of my editing within Emacs. I do not have to save files for the code to be evaluated, I just press a keystroke to evaluate the specific form I'm interested in. I can evaluate more fine-grained sections of code, not only entire files.

Pressing a keystroke is all it takes to save a file.

Also if you are selectively executing parts of files, how is it that you are editing the live running source code?