Free42 NSTK ENTER behavior

[Thomas Okken]

(03-19-2021 01:40 PM)fqz Wrote:  Since the topic of emulating RPL behavior was mentioned, I'm curious, does anyone have an example off-hand of an RPL calculator that enters input directly onto the "1:" level of the stack instead of an intermediate, anonymous input buffer?

That's what NSTK does, which is already a sort of odd hybrid I think, but admittedly it is unlikely to cause any change in practical behavior as opposed to the [ENTER] mapping, especially on a calculator like Free42 that doesn't support program entry in the main mode.

What NSTK does, in terms of number entry, is really the same as what 4STK does, which in turn is the same as what all the HP RPN calculators do: numbers are entered directly into the X register. There is no separate input buffer, because the three kinds of things you can enter (numbers, ALPHA strings, and programs) each have their own dedicated storage areas and their own separate input modes.

The weird hybrid aspect comes from the fact that the way ENTER behaves on RPN calculators, designed to allow filling the stack easily, doesn't make sense with the dynamic stack. It makes more sense to have ENTER terminate number entry without duplicating X, leading to the same result as pressing ENTER to terminate number entry on an RPL calculator. And to complete the illusion, backspacing all the way executes DROP, so you're left with the stack in the same state it was in before, also like on an RPL calculator.