I have managed to create the most bizarre way to write a spreadsheet engine in Python.
I still need to polish some things, but here are the highlights:
Your formulas compile to C
C is inlined using Instant
Yes, that means you edit a cell in the GUI and you need to wait until gcc compiles the thing.
Is it going to be useful? Probably not. Is it cool? I say yeah.
I will polish it somewhat, create a sttandalone engine, and show it here.