Also: https://github.com/TodePond/DreamBerd

Booleans can be true, false or maybe. Technical info: Booleans are stored as one-and-a-half bits.

A lot of work has gone into making floating point numbers efficient and they cover 99% of use cases. In the rare case you really need perfect fractional accuracy, it’s not that difficult to implement as a pair of integers.

That’s basically how the Android app Tasker works. You do the programming through its UI, but when you export/share your tasks, they’re saved as xml