This is another problem which was already solved in the '70s on the PDP-10. https://en.wikipedia.org/wiki/TECO_(text_editor)#As_a_programming_language https://e

This is another problem which was already solved in the '70s on the PDP-10. https://en.wikipedia.org/wiki/TECO_(text_editor)#As_a_programming_language https://en.wikipedia.org/wiki/TECO_(text_editor)#As_a_progra... ;) So you're keen on making invalid states unrepresentable ? Boy do I have the technology for you.