The Stack (according to Free42 Manual)

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boessu
Posts: 15
Joined: Mon Jan 28, 2019 9:40 pm

The Stack (according to Free42 Manual)

Post by boessu » Fri Feb 01, 2019 2:53 pm

Hello all

I have just a question of understanding. I'm referring to the fine documentation of José Lauro Strapasson http://thomasokken.com/free42/42s.pdf

According to the chapter 2.8 The Stack, the HP 42s has the following behavior:
(...)
But since the calculator’s display has only two lines just x and y lines are visible. When you enter a number (say 2 ENTER) what happens is the following.

i) The content of lines t and z are lost.
ii) The content of line y goes to line t.
iii)The content of line x goes to line z.
iv)The content just entered goes to line y and line x.

So what you just entered appears twice. So if you do 2 ENTER + you will have 4 as answer. This is a feature, a bad feature I think, of the HP RPN style used by the 42S (also in the 33S, 12C, etc but not in the HP48 or 49).
(...)
There are really things I don't understand.
First of all: the described behavior of the stack xyzt according to i) - iv) is in my understanding completely different. If I have a look at the DM42, which always shows the whole stack (what a manifesto to RPN ;)), the stack ist simply some sort of lifo stack. There is no copying, deleting and moving around as described in that documentation.
My HP12C has the same behavior and as far as I remember my original HP11C had the same.

The second point is: he mentioned there is a better way to do RPN and it was implemented in HP48/49. Now if I look at my HP17Bii+ in RPN Mode, it seems exactly the same to me as it is in the other HP RPN's I had and have. So either this one has also a "bad" feature or there was just a short time where it was different.

Last but not least: What is bad on the behavior of these calculators? Maybe I just got too much used to the way it works so that I don't see the point anymore. :)

I hope that's not a question of faith... It's just I don't understand what José Lauro Strapasson tries to tell me there.

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akaTB
Posts: 298
Joined: Tue May 02, 2017 11:56 am

Re: The Stack (according to Free42 Manual)

Post by akaTB » Fri Feb 01, 2019 3:07 pm

boessu wrote:
Fri Feb 01, 2019 2:53 pm

I hope that's not a question of faith... It's just I don't understand what José Lauro Strapasson tries to tell me there.
It is really a question of faith.
José Lauro likes the RPL way, with the edit line; I am accostumed to, and prefer, the RPN way.
I can't stand the error that shows when you press <= on a 28/48/49/50 with an empty stack, for example

Religious wars are 'round the corner, you are warned... :lol:
Greetings,
    Massimo

-+×÷ left is right and right is wrong :twisted: Casted in gold

mezoganet
Posts: 49
Joined: Tue Jan 22, 2019 12:54 pm
Location: Tours, France

Re: The Stack (according to Free42 Manual)

Post by mezoganet » Fri Feb 01, 2019 4:17 pm

akaTB wrote:
Fri Feb 01, 2019 3:07 pm
...
I can't stand the error that shows when you press <= on a 28/48/49/50 with an empty stack, for example

Religious wars are 'round the corner, you are warned... :lol:
I can't stand neither that stupid error !

Thats why I bought a 42s after having a 28s.
HP33E, HP34C, HP41C, HP16C, HP28S, HP42S, HP48S, HP12C, HP35S, DM42, DM41L, DM15L and HP3000 @ work during 18 yrs as IT Mgr

grsbanks
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Re: The Stack (according to Free42 Manual)

Post by grsbanks » Fri Feb 01, 2019 4:28 pm

But this begs the question, why would you press [<--] if the stack is already empty? :)
Not SwissMicros staff, just an enthusiast.

mezoganet
Posts: 49
Joined: Tue Jan 22, 2019 12:54 pm
Location: Tours, France

Re: The Stack (according to Free42 Manual)

Post by mezoganet » Fri Feb 01, 2019 4:34 pm

grsbanks wrote:
Fri Feb 01, 2019 4:28 pm
But this begs the question, why would you press [<--] if the stack is already empty? :)
Animal reflex, RPN animal behavior before any computing ?

Remember : a real RPN stack is NEVER empty ;)
HP33E, HP34C, HP41C, HP16C, HP28S, HP42S, HP48S, HP12C, HP35S, DM42, DM41L, DM15L and HP3000 @ work during 18 yrs as IT Mgr

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Walter
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Location: Close to FRA, Germany

Re: The Stack (according to Free42 Manual)

Post by Walter » Fri Feb 01, 2019 5:31 pm

boessu wrote:
Fri Feb 01, 2019 2:53 pm
I have just a question of understanding. I'm referring to the fine documentation of José Lauro Strapasson http://thomasokken.com/free42/42s.pdf

According to the chapter 2.8 The Stack, the HP 42s has the following behavior:
(...)
But since the calculator’s display has only two lines just x and y lines are visible. When you enter a number (say 2 ENTER) what happens is the following.

i) The content of lines t and z are lost.
ii) The content of line y goes to line t.
iii)The content of line x goes to line z.
iv)The content just entered goes to line y and line x.

So what you just entered appears twice. So if you do 2 ENTER + you will have 4 as answer. This is a feature, a bad feature I think, of the HP RPN style used by the 42S (also in the 33S, 12C, etc but not in the HP48 or 49).
(...)
There are really things I don't understand.
First of all: the described behavior of the stack xyzt according to i) - iv) is in my understanding completely different. If I have a look at the DM42, which always shows the whole stack (what a manifesto to RPN ;)), the stack ist simply some sort of lifo stack. There is no copying, deleting and moving around as described in that documentation.
... It's just I don't understand what José Lauro Strapasson tries to tell me there.
What is described in the part you quoted is simply wrong. That author obviously hasn't understood RPN and either remains in this state still or is unable to edit his text. :roll: Back to 1972! Without HP-35 no HP-48... ;)
DM42 SN: 00041 --- Follower of Platon.

HP-35, HP-45, ..., HP-50, WP 34S, WP 31S, DM16L

cdmackay
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Re: The Stack (according to Free42 Manual)

Post by cdmackay » Fri Feb 01, 2019 8:07 pm

As someone noted recently, also remember that on the DM42 you can type 2 EXIT to enter 2 into X without it also being lifted into Y.
Cambridge, UK
41CL 12/15C DM15/16 71B 17B/BII/bII+ 28S 42S/DM42 48GX 50g 35s 30b/WP34S Prime G2
& Casios, Rockwell 18R :)

keithdalby
Posts: 544
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Re: The Stack (according to Free42 Manual)

Post by keithdalby » Fri Feb 01, 2019 8:59 pm

cdmackay wrote:
Fri Feb 01, 2019 8:07 pm
As someone noted recently, also remember that on the DM42 you can type 2 EXIT to enter 2 into X without it also being lifted into Y.
... for some unknown reason

rprosperi
Posts: 489
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Location: New York

Re: The Stack (according to Free42 Manual)

Post by rprosperi » Fri Feb 01, 2019 9:44 pm

akaTB wrote:
Fri Feb 01, 2019 3:07 pm
...
I can't stand the error that shows when you press <= on a 28/48/49/50 with an empty stack, for example
I truly believe that if HP had made an exception, and treated [<=] while having an empty stack as a NOP, then RPL would have been accepted by a much larger percentage of the RPN faithful, and likely even embraced by many of them, battleship h/w design notwithstanding. Of course these things are much easier to see looking backwards than forwards...

In my earliest attempts at teaching myself RPL on my 28S (yes, I waited for the improved model) this was by far the most frustrating behavior. The 'Too few arguments' error was annoying when pressing [Drop] too many times, but this model had a separate back arrow key, which was (correctly) quietly swallowed when pressed with an empty stack. When the 48SX reworked the [Drop] and [<=] functions, they forgot that clever little trick (to swallow extra [<=] presses quietly) and thus permanently annoyed lots of users, contributing greatly to the religious wars we see today.
--bob p

DM42: β00071 & 00282

Joe Horn
Posts: 10
Joined: Thu Oct 04, 2018 12:10 am

Re: The Stack (according to Free42 Manual)

Post by Joe Horn » Sat Feb 02, 2019 4:42 am

Walter wrote:
Fri Feb 01, 2019 5:31 pm
boessu wrote:
Fri Feb 01, 2019 2:53 pm
I have just a question of understanding. I'm referring to the fine documentation of José Lauro Strapasson http://thomasokken.com/free42/42s.pdf

According to the chapter 2.8 The Stack, the HP 42s has the following behavior:
(...)
But since the calculator’s display has only two lines just x and y lines are visible. When you enter a number (say 2 ENTER) what happens is the following.

i) The content of lines t and z are lost.
ii) The content of line y goes to line t.
iii)The content of line x goes to line z.
iv)The content just entered goes to line y and line x.

So what you just entered appears twice. So if you do 2 ENTER + you will have 4 as answer. This is a feature, a bad feature I think, of the HP RPN style used by the 42S (also in the 33S, 12C, etc but not in the HP48 or 49).
(...)
There are really things I don't understand.
First of all: the described behavior of the stack xyzt according to i) - iv) is in my understanding completely different. If I have a look at the DM42, which always shows the whole stack (what a manifesto to RPN ;)), the stack ist simply some sort of lifo stack. There is no copying, deleting and moving around as described in that documentation.
... It's just I don't understand what José Lauro Strapasson tries to tell me there.
What is described in the part you quoted is simply wrong. That author obviously hasn't understood RPN and either remains in this state still or is unable to edit his text. :roll: Back to 1972! Without HP-35 no HP-48... ;)
Sorry to disagree, but everything said about the stack in the quote above is correct, as can be seen by simply doing what he says, for example:

Fill the stack with 9, 8, 7, 6 (so Z=9 and X=6) [EDIT: Oops; that should say T=9, not Z=9]
Press Roll-down 4 times to verify these contents.
Now press 2 ENTER (as he said to do).
The stack is now exactly as he said it would be, namely T=7, Z=6, Y=2, and X=2, with Z and T having been lost.
Last edited by Joe Horn on Sat Feb 02, 2019 1:03 pm, edited 1 time in total.

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