Bye bye Prime

[rprosperi]

(08-28-2014 05:44 PM)Joe Horn Wrote:  

(08-27-2014 11:42 AM)walter b Wrote:  Well, basically RPN features a finite stack, RPL an infinite stack. KISS.

If that's the defining difference, then the HP Prime is an RPN machine, not an RPL machine, because Prime's RPN stack is 128 levels high, no more, regardless of amount of memory available. ;-)

I'm curious, what happens when you try to enter the 129th item? I'm sure you checked, and my Prime is not with me.

[Michael]

(08-27-2014 06:11 PM)sol740 Wrote:  I'm considering buying a Prime - is it really as bad as people are saying here?

Have a look at: http://www.tricider.com/brainstorming/2eKfifdjarx

[Joe Horn]

(08-28-2014 05:48 PM)rprosperi Wrote:  

(08-28-2014 05:44 PM)Joe Horn Wrote:  ...Prime's RPN stack is 128 levels high, no more, regardless of amount of memory available.

I'm curious, what happens when you try to enter the 129th item? I'm sure you checked, and my Prime is not with me.

Same as traditional RPN: the top level gets pushed off the top of the stack and is lost. However, unlike traditional RPN, Prime's top level does not automatically replicate.

EDIT: By the way, this limit of 128 levels is not an RPN-only limitation in Prime. ALL THREE of Prime's history stacks are 128 elements high, but in CAS and Home (Textbook or Algebraic entry modes) those 128 elements include both the inputs and the outputs, whereas in RPN it only includes the outputs. When there are a total of 128 things on ANY history stack (RPN, Textbook/Algebraic, or CAS), putting something new on the bottom of the history stack pushes the top element off that stack and loses it.

[walter b]

(08-28-2014 05:44 PM)Joe Horn Wrote:  

(08-27-2014 11:42 AM)walter b Wrote:  Well, basically RPN features a finite stack, RPL an infinite stack. KISS.

If that's the defining difference, then the HP Prime is an RPN machine, not an RPL machine, because Prime's RPN stack is 128 levels high, no more, regardless of amount of memory available. ;-)

Thanks for that information - I didn't know that before. I thought of Wickes' RPL. Seems my definition was too simple then. Would "RPN features a finite stack with top level repetition and roll" be better to differentiate between RPN and RPL?

d:-)

[Don Shepherd]

(08-28-2014 08:55 PM)walter b Wrote:  

(08-28-2014 05:44 PM)Joe Horn Wrote:  If that's the defining difference, then the HP Prime is an RPN machine, not an RPL machine, because Prime's RPN stack is 128 levels high, no more, regardless of amount of memory available. ;-)

Thanks for that information - I didn't know that before. I thought of Wickes' RPL. Seems my definition was too simple then. Would "RPN features a finite stack with top level repetition and roll" be better to differentiate between RPN and RPL?

d:-)

I always thought the principle difference between RPN and RPL machines was in the programming: RPN machines (65, 12c, 32sii) used easy-to-understand keystroke programming while RPL machines (48, 49) used those weird commands like <dup> <dup> and so on, which I never took the time to learn although I admit it seems to be a powerful system.

[Joe Horn]

(08-28-2014 08:55 PM)walter b Wrote:  Would "RPN features a finite stack with top level repetition and roll" be better to differentiate between RPN and RPL?

<opinion>

RPN and RPL are not mutually exclusive concepts. RPL is a Language that uses RPN Notation, just as FOCAL is a Language that uses RPN Notation. One universally recognized hallmark of RPN is adding 2 plus 3 to get 5 by executing 2 3 +. Both the HP-41 and the HP 50g do this, so they are both RPN machines according to that hallmark. The user interface is different, sure, but the Reverse Polish Notation is the same, so they are both RPN. RPN is not a user interface; it is a mathematical notation. RPN can be (and has been) implemented in many different user interfaces.

Many names have been proposed for these various implementations of RPN, but I don't think HP ever adopted any of those names officially, and none of them have really "stuck" in the user community. Until that happens, awkward things like "X-entry RPN" and "command-line 4-level RPN" and "infinite-stack RPN" and "Prime RPN" will need to be spelled out to avoid ambiguity.

We really, really, really need permanent, unambiguous, universally adopted NAMES for all these various RPN's. And PLEASE don't entertain the idea that any one of them is TRUE RPN. They ALL are "true RPN". Why? Because if you do 2 3 + to get 5, it's truly Reverse Polish Notation, so it's true RPN. The rest is details... details which hopefully some day can be clearly represented by meaningful, unambiguous, non-judgmental names for their respective RPN implementations.

</opinion>

[rprosperi]

(08-28-2014 10:42 PM)Joe Horn Wrote:  ...represented by meaningful, unambiguous, non-judgmental names for their respective RPN implementations.

Oh, that's easy.

Oh wait; meaningful, unambiguous and non-judgemental? No it's not easy, it's not even hard, it's all but impossible to meet those criteria, which I agree are excellent goals.

Which of course is why these names have never emerged, despite 30+ years of real smart folks trying to make them.

It seems in everyday usage here on the MoHPC Forums, most folks know what one means pretty accurately when one uses "RPL" (it's either 'that powerful language and programing model used on the 48/49/50 that I love' or 'that powerful language and progrmaming model used on the 48/49/50 that I hate'), but the confusion is rampant when one uses "RPN" as it implies most of HP's machines, as several folks have noted here.

I never thought about this way before, but Walter may have captured the essence of what is 'classic' RPN by adding 'top level replication and roll'.

To me personally, that meets your 3 criteria, but impossible to speak for everyone on that point. And this is my point.

Interesting new views on an old topic!! Thanks for that gents.

[Joe Horn]

(08-28-2014 11:27 PM)rprosperi Wrote:  I never thought about this way before, but Walter may have captured the essence of what is 'classic' RPN by adding 'top level replication and roll'.

Unfortunately, even that phrase is ambiguous; it doesn't distinguish between X-entry RPN and some recent 4-level entry line RPN models which also have top level replication and roll, e.g. the HP 20b and 30b in RPN mode. For example, in classic RPN, 1 ENTER 2 ENTER + yields 4, but it yields 3 on the HP 20b and 30b. Also, on the 20b and 30b, Clear stack, 5 ENTER CE (clear entry) 6 ENTER results in 0, 0, 0, 6 on the stack, whereas in classic RPN you'd get 0, 5, 6, 6. Huge difference. But they both have top level replication and roll. So that's not a defining difference.

[eried]

(08-28-2014 05:44 PM)Joe Horn Wrote:  because Prime's RPN stack is 128 levels high

So the Prime is \[(RPN)^{3.5}\]

[walter b]

(08-28-2014 10:05 PM)Don Shepherd Wrote:  RPN machines (65, 12c, 32sii) used easy-to-understand keystroke programming while RPL machines (48, 49) used those weird commands like <dup> <dup> and so on, which I never took the time to learn although I admit it seems to be a powerful system.

I concur, though that seems a necessary but not sufficient condition.

d:-)

[walter b]

Ok, let's try to structure the mess a bit (just by heart, I don't have any machine at hand right now):

1. From the HP-35 to the HP-42, I'd say, RPN was unambiguous in the HP world: 4 levels, top level repetition, roll - I suggest calling that classic RPN.
2. With the HP-28 and -48, infinite stack appeared and RPN was changed to RPL - that powerful UI that Don, Valentin, and others love so much.
3. Recently (i.e. with the HP-20b and -30b, but maybe more) a RPN dialect appeared featuring 4 stack levels plus an entry register as introduced with RPL.
   

I hope these are all the basic categories. They will need some polishing certainly.

d:-)

[lmmt61]

For me, RPL is equivalent to a graphical screen showing several stack lines and with the capacity to put in those lines numbers, variables, programs, etc., altogether. I know that RPL is more related to the programming language but I identify a RPL machine with the other posibilities I have mentioned.
RPN calculators are more related to 1 or 2 screen lines with a limited stack and without the mixture of objects in the stack, at leas not as explicit as with RPL. Of course the programming method is also different.
I really prefer RPL calcs because of the "side effects" (bigger screen, memory, stack, etc.) coming with it.

[walter b]

BTW, that definition / categorization is independent of the physical size and shape of the device under investigation. E.g. with the 43S, you'll get RPN on a multiline display.

And there is a test case to find out what you have (kudos to hansklav):

1 ENTER 2 ENTER 3 ENTER 4 ENTER 5 ENTER 6 ENTER 7 ENTER 8 ENTER 9 ENTER
+ + + + + + + + (8 times)

Now, if you get

• 68 then you've got type 1 (classic RPN) with 4 stack levels,
• 54 then you've got type 1 (classic RPN) with 8 stack levels,
• 45 then you've got type 2 (RPL) with a large ('infinite') stack,
• 60 then you've got type 3 with 4 stack levels.
  

d:-)

[Eric Rechlin]

Perhaps an unambiguous term for the input method is just "postfix input". That covers all variations of RPN, RPL, and everything in between.

[peacecalc]

Hello folks,

for me it seems the thread has changed his contents, it is not longer a thread about a possibly ugly machine (not only in a aesthetic way), but a thread about the meaning of RPL, RPN, NLP and so on...

Maybe it would be a good idea to split this thread in two different ones...

Greetings
peaceglue

[walter b]

I agree. But who can do it? Also cutting through that messy reply structure?

d:-?

[René Franquinet]

(08-27-2014 10:19 AM)walter b Wrote:  

(08-27-2014 10:09 AM)Dave Dirckx Wrote:  Fortunately I can fall back to the 50G and other models to enjoy a reliable HP RPN calculator.

The 50G is RPL, not RPN.

d

I thought the RPL is the programming language of the 50G, which of course is effectuated in RPN.

[hansklav]

(08-28-2014 10:42 PM)Joe Horn Wrote:  (…) We really, really, really need permanent, unambiguous, universally adopted NAMES for all these various RPN's (…) which hopefully some day can be clearly represented by meaningful, unambiguous, non-judgmental names (…)

In my (still not entirely finished) RPN Tutorial in Appendix G on RPN Variants I propose the following scheme:

Purely looking at the workings of the stack of RPN calculators (and not at their programming capabilities) a few RPN variants can be discerned. Both the bottom and the top of the stack may vary.
A. Bottom of the stack:

1. Classical RPN
2. Entry RPN
   

B. Top of the stack:

1. Small stack (4-, 5- or 8-level) with ‘top copy on pop’
2. Very large stack (>100 levels), no ‘top copy on pop’
   

Four types of RPN

All four possible combinations of the 2 × 2 possibilities of RPN variants actually do exist, although not always in hardware:

α. (alpha type) The combination of Classical RPN with a small stack and ‘top copy on pop’ is well known. Besides the 4-level stack of all classical HP RPN calculators (all HP RPN calculators except those listed below after β. and γ.) and their emulations there is the 5-level stack of the Heathkit OC-1401, and the 8-level mode of the WP 31S and WP 34S.

β. (beta type) All HP RPN graphing calculators (series 28, 48 & 49, the HP 50g and Prime) have Entry RPN and an unlimited or very large stack (128 stack levels in the Prime).

γ. (gamma type) The HP 20b and HP 30b have Entry RPN and a 4-level stack with ‘top copy on pop’.

δ. (delta type) The Calculator application in Mac OS X in RPN-mode combines Classical RPN behaviour of the ENTER key with an unlimited stack.


Discussion

Following Richard Nelson in his article in HP Solve (#27 p. 42) ‘RPN Evolves’ the terms Classical RPN and Entry RPN only refer to the differences at the bottom of the stack. I think Classical RPN is better here than Classic RPN because the latter term denotes a judgement (‘of the highest quality and outstanding of its kind’) whereas Classical RPN is purely descriptive, as in ‘classical music’ (formal music adhering to certain stylistic principles of the late 18th century).

This scheme is unambiguous and non-judgemental, and can be used for future implementations with different programming languages because it does not say anything about programming capabilities. And it conveys some meaning because it indicates the chronology and link to HP of the RPN variants, α type being the oldest, β type younger and γ type the youngest RPN variant first implemented by HP; and δ type another, non-HP type. The 3-level RPN of the HP series 9100 en 9800 could be called ‘pre-α type’.

Just my two cents.

Hans

[Didier Lachieze]

(08-29-2014 09:24 AM)walter b Wrote:  And there is a test case to find out what you have (kudos to hansklav):

1 ENTER 2 ENTER 3 ENTER 4 ENTER 5 ENTER 6 ENTER 7 ENTER 8 ENTER 9 ENTER
+ + + + + + + + (8 times)

Now, if you get

• 68 then you've got type 1 (classic RPN) with 4 stack levels,
• 54 then you've got type 1 (classic RPN) with 8 stack levels,
• 45 then you've got type 2 (RPL) with a large ('infinite') stack,
• 60 then you've got type 3 with 4 stack levels.
  

d:-)

There are a few other RPN flavors.
For example, if you get

• 81 then you've got a calculator with 3 stack levels and Y as the accumulator, such as the HP 9100A/B or HP 9810
• 26 then you've got a calculator with 3 stack levels and no top level replication, such as the NS 4510
• 33 then you've got a( calculator with 4 stack levels and no top level replication, such as the NS 4640
  

Edited to fix the result for the HP 9100 & 9810. Edited again to revert to the original number for the HP 9100.

[hansklav]

(08-30-2014 12:22 AM)Didier Lachieze Wrote:  

(08-29-2014 09:24 AM)walter b Wrote:  And there is a test case to find out what you have (kudos to hansklav):

1 ENTER 2 ENTER 3 ENTER 4 ENTER 5 ENTER 6 ENTER 7 ENTER 8 ENTER 9 ENTER
+ + + + + + + + (8 times)

Now, if you get

• 68 then you've got type 1 (classic RPN) with 4 stack levels,
• 54 then you've got type 1 (classic RPN) with 8 stack levels,
• 45 then you've got type 2 (RPL) with a large ('infinite') stack,
• 60 then you've got type 3 with 4 stack levels.
  

d:-)

There are a few other RPN flavors.
For example, if you get

• 81 then you've got a calculator with 3 stack levels and Y as the accumulator, such as the HP 9100A/B or HP 8010
• 26 then you've got a calculator with 3 stack levels and no top level replication, such as the NS 4510
• 33 then you've got a calculator with 4 stack levels and no top level replication, such as the NS 4640
  

I don’t have access to an early HP desktop calculator, but judging from the manual I would expect one of the HP 9100 or 9800 series to produce 72 in this test.
Who can do the test on the hardware?

Hans