|Re: 35S vs 30b Stack|
Message #23 Posted by Bart (UK) on 14 Sept 2011, 8:51 a.m.,
in response to message #20 by Thomas Radtke
I started HP life with the 28S, and there's nothing inconsistent in the RPL stack operation. Actually it is more consistent.
Sorry Thomas, you don't seem to understand the fundamental difference. As I said in my reply to Walter's post, the old RPN stack used the X-regiter as an input register as well. Therefore, when you hit Enter, the value is copied into the Y-register, why?, because for the next entry, the X-register is overwritten because it is the input register. The so-called RPL stack has a separate input register, that is why the need to copy the input value to the Y-register is not necessary when hitting Enter. The input register only exists during input (for obvious reasons), so hitting '+' operator with an input active, operates on the input and first stack item. When there is no active input, hitting '+' operator operates on the first stack item and second stack item.
Quote:I hope my explanation makes it clear that X is not edited, why it's not necessary & what it is doing.
This is very confusing, since you would assume from the first action that x is edited, and thus the latter should give 4, which is not the case on RPL machines.
Quote:How so? As I explained, when input is active, the input register is used as the first argument (or the only argument in a 1 argument operation).
Sometimes a secret stack lifting has to happen in RPL, such as when an operator is used while editing a number.
Unless you are actually referring to editing the first stack line after it was entered - then you have effectively removed the item from the stack and it will only be put back when you finish editing. SO, if you use an operator while edit is active, it will work on whatever was above the item being edited, because that item was removed from the stack while editing. You can't complain about this behaviour, because such a mode did not exist on RPN calculators anyway.
Quote:You ENTER two numbers that you want to operate on, but end up operating on the last number AND a copy of the last number. That's transparent? I want numbers A and B, whether I hit ENTER or not. BEFORE hitting ENTER, a number is not on the stack. Now I to put both A and B on the stack, then operate. So after actually putting B on the stack (by hitting ENTER - it is not officially ON the stack until then), I now have a COPY of B in Y??? Now THAT's inconsistent, but because people have learnt to live with it, they call it consistent? or "the way"?
I see no disadvantage with RPN, but one huge advantage: Transparency of operation.
As you rightly commented, Pauli has to mimic the "RPN" behaviour using "RPL" type stack because people don't want to change, are unwilling to adapt, not moving with modern technology, etc. etc.
Again, as always, just my 2p worth.
Edited: 14 Sept 2011, 8:55 a.m.