[mhh__]

The book "Electronic Design automation" by Wang, Chang, and Cheng is quite approachable.

The reason why they are opqaue is partly because the problem is hard, and secondly because the developers of the code make money directly off the tools (like compilers were in the past)

[User23]

Physical layout CAD software is really interesting though and heavily scriptable. I’m pretty sure at least one major offering uses some kind of lisp as its extension language.

[monocasa]

A lot of the were written fully in lisp back in the day, and might still be underneath it all. ie. it might be more than just being used as an extension language.