RPN83P: RPN calculator for TI-83+ TI-84+ inspired by HP-42S

[jthole]

Not a bug, but something that surprised me:

lSTK(1) only contains the X register after an operation is performed on it. That is contrary to what I would expect in a HP 42S.

But of course that’s only visible when looking at the calculator from the outside.

As an example:

After I cleared the stack, I enter 1 and exit the RPN app. lSTK(1) contains 0.
When I go back, press (X^-1), and examine the first element in the STK list, it contains 1, as expected.

Again, not a bug, but unexpected when you think lSTK would reflect the current stack state.

Simple resolution: if you want to use any other value than LastX outside of the RPN app, store it in a register (the lREGS list).