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[34S] Proposal for Entry RPN mode with dynamic stack
02-18-2015, 09:45 PM
Post: #38
RE: [34S] Proposal for Entry RPN mode with dynamic stack
Not that it cannot be done, but at what cost?


I do understand the (almost) unlimited stack of the 28C and its descendants with at least some of the stack levels visible. And I do understand the fixed level stack of what is called classic RPN here. The former has a unique feature: a variable (and countable) number of values on the stack, including the empty stack. A fixed stack simply doesn't care how many values the user has ever pushed. Whether the fixed stack contains garbage or useful data is completely open to interpretation. (I'm undecided about the whole stack lift business, I'm just talking about the stack depth).

A possible mixture of these modes as is the topic of this thread will lose either of the clear concepts. You cannot determine the number of values on the stack if its less then the fixed size of the "base" stack. You cannot recall arbitrary stack levels if they are beyond register D. You will (quickly, due to the limited resources of the platform) lose data off the top of the stack without notice, or, depending on implementation, will be confronted with an error message which is annoying if you just don't care about the "garbage" you pushed earlier. And all this happens "in the blind" because of the famous display.

KISS! Keep It Short and Simple!

BTW, fell free to implement anything you want and share the results with others, it's an open platform. Wink And don't forget to implement proper error handling which restores the stack to its state before the error occurred.

Marcus von Cube
Wehrheim, Germany
http://www.mvcsys.de
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RE: [34S] Proposal for Entry RPN mode with dynamic stack - Marcus von Cube - 02-18-2015 09:45 PM



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