Ooh that is very cool, it really shows off how great stacks are as a construct. Its quite fun that a good way of performing infix maths is just to convert it to RPN
Mixed-fractions, decimal/fraction conversion, and some misc functions are on the TODO list in my head. I probably also need to add variables, as currently the result is just printed out?
I actually just treat everything as a fraction, so there's not really a concept of separate digits. Its all just reciprocals