Cool, thanks for sharing indeed! I enjoyed the entry on your devlog. It seems a bit like Lisp but with a Smalltalk environment? It struck me that it immediately evaluates a form (I guess only the top-level one?) without even pressing enter.
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Xerox designed both of those, so it's from the same company that pioneered Smalltalk. And it works in a similar way. I think they were being co-developed around the same time. Yes, The Programmers Assistant (REPL) enters an expression as soon as you close it off. If you type in a ] it will close it off immediately and finish all the parentheses.