Question - Why invent a language syntax instead of building a powerful tool that leverages an existing language?

[DeflateAwning]

[IamTheCarl]

There are generally three reasons.

1. I couldn't find a practical way to fit the unit typing to literals (that 10mm syntax). I looked into Python, Lua, and Rhai. We could have just made units a new type for these languages, like say measurement.new(10, "mm"), but that just felt... clunky. The Rust library uom (from which I took a lot of inspiration) does something similar to this, and that's where I got to experience working with a system like that. I will admit that I did not research JavaScript or TypeScript.

2. Scripting languages don't play well with threads. Typically you'll have some kind of global interpreter that has to be locked behind a Mutex (see Python's GIL). With Lua and Rhai you can put an independent interpreter on each thread, but then you have to figure out some complex data juggling and the tradeoffs are questionable. I've yet to see it done well and I don't think I could do better.
   Command CAD models aren't really scripts, but are more like tree structures. They have a lot in common with Json in that aspect. With most branches being able to run in parallel. CommandCAD currently does make use of this. This was directly inspired by how the Nix configuration language works (which also gets a lot of criticism for not just using an existing language)

3. It's just been done already and I don't think I could make it better than what's already out there. There are more CAD frameworks for Python than I have fingers (don't worry, I have all 10 of them). Despite that, none of them have approached the level of popularity that OpenSCAD and FreeCAD see (and those don't even compare to the proprietary tools). I don't know why exactly that is but I have tried two of the more popular ones (CAD Query and Build123D) and found their workflows to be... clunky feeling in comparison to OpenSCAD. That's all opinion though so I'll keep my thoughts on those to myself.

I guess I'll wrap this up with the following: Command CAD has been a very selfish project. I made it entirely for myself. I doubt I'd ever get sponsors and I don't really need sponsors, so I'm making it exactly what I want a CAD program to be. I wanted a fully declarative CAD with unit literals, dimensional type safety, and imperative modeling. I made it open source in hopes that if other people like it, they'd contribute back into it to improve the feature set. If that never happens, I don't care. I still got a CAD program that I like out of this.

[DeflateAwning]

Great answers, thank you!