I mean I would probably punch that in as x 2 * 1 + (-) 3 + x % When I was using my rpn calculator. (-) flips the sign of the number on top of the stack.

I mean I would probably punch that in as x 2 * 1 + (-) 3 + x % When I was using my rpn calculator. (-) flips the sign of the number on top of the stack. Or use flip -. But you can avoid growing the stack long enough to be confusing.