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Full Version: HP35s: unexpected behaviour with LASTx
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Some time ago I found a somewhat strange behaviour of my 35s with LastX and Pi.
Maybe you can try this:

Code:
```2 [ENTER] 5 [x]           10,0000 3 [LASTx] [x]             15,0000```

So far, so good. After the first multiplication LASTx was set to the last factor 5, so the second calculation returned 3x5 = 15.

Now do the same with Pi instead of 3.

Code:
```2 [ENTER] 5 [x]           10,0000 [π] [LASTx] [x]           31,4159```

After pressing [LASTx] not the expected 5 appears, but the last result 10. It actually looks like pressing the [π] key causes the current X to become the new LASTx. So the result is not the expected but 10π.

You may even try this:

Code:
```[CLSTK] [x]              0,0000   clears the complete stack including LastX 123 [π]                  3,1416   enters 123 and Pi [LASTx]                123,0000   obviously 123 has been moved to LastX```

BTW this does not seem to happen with other constants, e.g. in the first example, [e] [LASTx] [x] returns e*5 = 13,5914.

Any ideas what's going on here?
May this be a firmware bug that sets LASTx when π is entered?
The 35s seems to behave as if π was a function π(x).

Dieter
Hello Dieter,

AFAIK this behaviour complies with the description found in appendix B.6 of the user's guide (page 306 in the PDF file):

Quote:The Status of the LAST X Register
The following operations save x in the LAST X register in RPN mode:
+, –, × , ÷
...

followed by a list of mathematical and conversion functions, but not including [pi]. That gives no explanation why [e] does save x whereas [pi] does not. Perhaps [pi] behaves in a different way, because it's invoked as a keystroke function (not included in the list above) in contrast to the other constants invoked from within the CONST menu and pushed to the stack just like any normal number typed in via the keyboard.
Bug confirmed, not present on my HP 33S.
Added to the bug list.

Pauli
(11-20-2015 07:58 PM)renif Wrote: [ -> ]AFAIK this behaviour complies with the description found in appendix B.6 of the user's guide (page 306 in the PDF file):

The point is that it's exactly the other way round: Pi seems to set (and overwrite) LastX. So the calculator is working not as described in the manual. The manual says that Pi does not affect LastX, while actually it does.

BTW unlike any other HP I know of.

Dieter
Dieter, considering that you've invested quite some time programming the 35s, do you think there might be more clowns in this car?
(11-20-2015 08:41 PM)Marcio Wrote: [ -> ]Dieter, considering that you've invested quite some time programming the 35s, do you think there might be more clowns in this car?

We will never know. I have been using the 35s since it became available in 2007. But I discovered the last two entries on the "official bug list" not before this year, i.e. after eight years of use. I came across them during debugging programs that did not work as expected. But I have not used all the 35s functions yet... ;-)

Dieter
(11-20-2015 08:02 PM)Paul Dale Wrote: [ -> ]Added to the bug list.

Pauli

Sad... Yet another reason to hate (well... not trust) this machine. And it so much is one that I'd love to love. Though as Dieter implied, not finding this bug after 8+ years of use certainly does indicate it's not a critical or obvious issue, the nature of this one, like so many others, clearly imply the unit was not systematically tested prior to release; I'm sure there are more waiting to be found, and since most folks don't trust it, and therefore use it rarely, they will likely remain undiscovered for years to come.
The sad part is that HP decided that nothing will be done about it, apart from the fact that there might be many more bugs. Twenty-two so far!
Yes, Marcio, a sad state of affairs, 22 bugs & we don't know what may be lurking in the innards of the calculator.

On the other hand, 22's a modest number compared with the number of known bugs in the Prime - has anyone tired to compute the actual number of resident irritations anchored in the confines of the Prime? & they seem to be reproducing!
Well, at least they're releasing updates 2-3 times a year for the Prime. OTOH, If the number of bugs increases every time a update is released, it means something is not right there.

I haven't used it (or the emulator) for quite a while.

Marcio
I bet this is in the 33s too. Much of the troubles with the 35S were already trouble with the 33S.

Neither of these machines are worth serious use for real world computation. Just not worth it.
(12-04-2015 02:35 PM)Bill Platt Wrote: [ -> ]I bet this is in the 33s too. Much of the troubles with the 35S were already trouble with the 33S.

Neither of these machines are worth serious use for real world computation. Just not worth it.

See post #3
(11-20-2015 10:35 PM)Marcio Wrote: [ -> ]The sad part is that HP decided that nothing will be done about it, apart from the fact that there might be many more bugs. Twenty-two so far!

Why even bother compiling a list? HP won't do anything about it, nor would I expect them to for a disposable calculator. It's so cheap, it's not worth replacing the batteries. Just buy a new one.
The list was started soon after the 35S was available and back then we had no idea that that was it. We expected updated firmware fixing bugs. Hence the list.

Why maintain it now? No good reason. Bugs aren't being found quickly and it isn't much work, so I continue even though I don't have a 35S anymore.

- Pauli
(12-09-2015 08:45 PM)toml_12953 Wrote: [ -> ]Why even bother compiling a list? ....

Totally logical question.

Fully out of place here though, where logic is well down the list of reasons for doing many (most?) of the obsessive things we do with, for and about HP calculators.
(12-09-2015 11:23 PM)rprosperi Wrote: [ -> ]
(12-09-2015 08:45 PM)toml_12953 Wrote: [ -> ]Why even bother compiling a list? ....

Totally logical question.

Fully out of place here though, where logic is well down the list of reasons for doing many (most?) of the obsessive things we do with, for and about HP calculators.

List of bugs is useful for forensic calculations & diagnosis of results.

Bug finders, please keep up the good work, list keepers too.
(12-04-2015 03:45 PM)Gerald H Wrote: [ -> ]
(12-04-2015 02:35 PM)Bill Platt Wrote: [ -> ]I bet this is in the 33s too. Much of the troubles with the 35S were already trouble with the 33S.

Neither of these machines are worth serious use for real world computation. Just not worth it.

See post #3

To make this even more confusing, there is more than one 33S ROM! They have different behavior--at least in ALG mode...I wrote about this a looooong time ago. I can't even remember the details.
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