Is RPN still relevant?

[Thomas Klemm]

(12-23-2023 12:23 AM)Matt Agajanian Wrote:  Talk about outrageous going rates!!

Compared to a new one from Easycogo, this is a bargain.

[cdmackay]

If we look at sold prices, rather than listings, eBay UK shows several 35s recently between £50–90.

[3298]

(12-21-2023 01:27 PM)rprosperi Wrote:  The incomplete question "Is RPN still relevant?" is simply not clear enough for any kind of consensus, as the disparate and diverse replies show.

Is RPN still relevant for the public at large?

Is RPN still relevant for high-end calculator users?

Is RPN still relevant for readers of this MoHPC Forum?

Is RPN relevant for American (or substitute UK, EU, China, Indonesian, 3rd-world, etc.) school children?

are all questions that might reasonably be debated, likely with differing conclusions, but as initially asked is so wide open as to be impossible to reach a conclusion.

This separation into different domains is indeed important, thank you. While I have nothing to add on the latter three domains, the "public at large" one is in need of some addition.

In certain (admittedly somewhat niche) topics reverse polish notation remains relevant, maybe even inescapable. The one that immediately comes to my mind is parsers (for programming languages, mathematical expressions, etc). Case in point: just yesterday independent game development studio Wube Software released a blog post in their Factorio Friday Facts series containing the following tidbit with a mention of RPN.

FFF-390 Wrote:The parser was split into three logical parts.

1. Tokenizer, which processes a stream of characters and categorises individual character groups to token types. The operator character set is based on Lua with a few exceptions where both C++ and Lua syntax are supported. Apart from regular numbers, it supports scientific notation, and other formats can be added as needed.
2. PostfixTokenizer, which converts infix tokens to postfix (reverse Polish) notation. This step is responsible for following operator precedence rules and for making sure that resulting expressions are unambiguous. It uses a modified version of the shunting yard algorithm to process data.
3. NoiseExpressionParser, which takes postfix tokens and converts them to a noise expression tree (AST).

(Original post here.)

Ironically the need for a parser means modern algebraic calculators likely contain some RPN deep inside their bowels. You'd have to get their firmware source code or engage in an excessive amount of reverse engineering to find it, but there's a very good chance it's there.

Outside the world of calculators, here's a piece of what Clang can spit out when instructed to print the Abstract Syntax Tree of a C program. In particular, this is a function call.

Code:

|   |-CallExpr 0x559193b5a4b0 <line:19:1, col:41> 'void'
|   | |-ImplicitCastExpr 0x559193b5a498 <col:1> 'void (*)(struct list *, void *)' <FunctionToPointerDecay>
|   | | `-DeclRefExpr 0x559193b5a3e0 <col:1> 'void (struct list *, void *)' Function 0x559193b597c8 'appendToList' 'void (struct list *, void *)'
|   | |-ImplicitCastExpr 0x559193b5a4e0 <col:16> 'struct list *' <LValueToRValue>
|   | | `-DeclRefExpr 0x559193b5a400 <col:16> 'struct list *' lvalue Var 0x559193b5a0d8 'l' 'struct list *'
|   | `-ImplicitCastExpr 0x559193b5a4f8 <col:27> 'void *' <LValueToRValue>
|   |   `-DeclRefExpr 0x559193b5a420 <col:27> 'void *' lvalue Var 0x559193b5a020 'elem' 'void *'

Printed this way, it looks more similar to RPN's sibling Polish Notation, but the Reverse part is just a matter of traversing the same AST differently (parent nodes after their children instead of before). In code generation there's bound to be a part processing this into instructions to place parameters onto the target processor's stack, followed by the instruction to actually issue the call. It'll be obscured by handling for (platform-specific) register-passed parameters and other optimizations, of course, but if you can look past that, you'll recognize the RPN basics even in this widely used program.

Other compilers similarly have a pinch of RPN (or maybe in some cases just PN) in them. And in the world of academia, the compiler-adjacent automata theory works with a stack once you move past type 3 automata in the Chomsky hierarchy into type 2, This stack obviously lends itself to RPN style utilization. Types 1 and 0 correspond to Turing machines (with a certain limitation for type 1), with a tape memory instead, but that could be described as two stacks (one in each direction of the type head), or maybe as a stack you can ROLL like we do in RPL.
Either way, deep within computers, RPN is lurking. Not many people dig that deep anymore (which I think is a problem as it easily leads to misconceptions), but once you need to, you'd be better off if you can wrap your brain around RPN.

[Peet]

(12-21-2023 01:27 PM)rprosperi Wrote:  Is RPN still relevant for the public at large?
Is RPN still relevant for high-end calculator users?
Is RPN still relevant for readers of this MoHPC Forum?
Is RPN relevant for American (or substitute UK, EU, China, Indonesian, 3rd-world, etc.) school children?

Sure, but unfortunately many of them don't know it.

[Steve Simpkin]

(12-23-2023 08:22 PM)cdmackay Wrote:  If we look at sold prices, rather than listings, eBay UK shows several 35s recently between £50–90.

The HP 35s models actually "Sold" on the U.S. eBay seem to be selling for a lot more.
Recent New-in-package sold ones seem to range around $300 to $400 USD, perhaps averaging around $340 (£270).

Recent used sold ones seem to range from $170 to $320 USD, perhaps averaging around $250 (£197).

https://www.ebay.com/sch/i.html?_nkw=HP+...ld=1&rt=nc

[Raymond Del Tondo]

(12-23-2023 11:44 PM)Peet Wrote:  

(12-21-2023 01:27 PM)rprosperi Wrote:  Is RPN still relevant for the public at large?
Is RPN still relevant for high-end calculator users?
Is RPN still relevant for readers of this MoHPC Forum?
Is RPN relevant for American (or substitute UK, EU, China, Indonesian, 3rd-world, etc.) school children?

Sure, but unfortunately many of them don't know it.

As it seems to be clear that RPN sits in an elitary niche (those who know and those who don't;-) ,
I may narrow the question to: Is RPN still relevant to you (or me)?

For me, I can anwer that question with YES!
Be it an HP-32S, HP-41, HP-42S with traditional 4-level+LastX stack, or a more advanced RPN implementation like in the HP 48 (*) or some of its relatives.

Even the poor RPN implementation in the Prime may be sufficient for some.

An alternative and specialized RPN environment for the Prime is the RPN SurveyCalc by Jacob Wall.

(*) Don't confuse the HP 48 RPN stack user interface with the RPL programming system.

[Matt Agajanian]

On the lookout for a 33S and on the subject of the outrageous, here’s a doozy:

Now THIS is outrageous!!

[dm319]

(12-23-2023 11:36 PM)3298 Wrote:  Ironically the need for a parser means modern algebraic calculators likely contain some RPN deep inside their bowels.I'm not a computer scientist, but

Not a computer scientist, but I assumed that all CPUs worked by getting the numbers first, then doing the thing on them (add, shift etc). At least that is how assembly looked like to me.

[ijabbott]

(12-24-2023 11:32 AM)dm319 Wrote:  

(12-23-2023 11:36 PM)3298 Wrote:  Ironically the need for a parser means modern algebraic calculators likely contain some RPN deep inside their bowels.I'm not a computer scientist, but

Not a computer scientist, but I assumed that all CPUs worked by getting the numbers first, then doing the thing on them (add, shift etc). At least that is how assembly looked like to me.

Depending on the CPU, the fetched instruction may encode both the operation and one or more of the operands, (which may be an immediate value, a direct or indirect memory location (with absolute or relative address), or a register).

[cdmackay]

(12-24-2023 12:52 AM)Steve Simpkin Wrote:  

(12-23-2023 08:22 PM)cdmackay Wrote:  If we look at sold prices, rather than listings, eBay UK shows several 35s recently between £50–90.

The HP 35s models actually "Sold" on the U.S. eBay seem to be selling for a lot more.
Recent New-in-package sold ones seem to range around $300 to $400 USD, perhaps averaging around $340 (£270).

Recent used sold ones seem to range from $170 to $320 USD, perhaps averaging around $250 (£197).

https://www.ebay.com/sch/i.html?_nkw=HP+...ld=1&rt=nc

That's weird; at those prices, folks ought to look to eBay UK and pay shipping and any import duties, perhaps.

[avsebastian]

[/quote]

A 50gii would be cool, but I hope the 35s (or something similar) is resurrected before that. It is unfortunate that the 2 RPN calculators approved for the FE exams are out of production. The prices for the 35s on eBay are out of control.
[/quote]

But.... The hp 15C is similar or superior to hp 35s, or not ,for that exam?

[avsebastian]

(12-24-2023 11:19 AM)Matt Agajanian Wrote:  On the lookout for a 33S and on the subject of the outrageous, here’s a doozy:

Now THIS is outrageous!!

It' s a calculator or a bitcoin?

[trojdor]

I still use and appreciate the elegance of the RPN calculators, although I admit to also using several algebraics, as well.

And it still catches students by surprise, when I can use an RPN calculator to calculate 4 resistors in parallel with 8 keystrokes (not counting digits).

This was my explanation as to why I frequently preferred RPN;

"This is your father's HP. This is the calculator of a Jedi Knight. Not as clumsy or random as algebraic. An elegant tool, for a more... civilized age."
— With apologies to Obi-Wan Kenobi, Star Wars: A New Hope


mike

[cjsuk]

Regarding the prices of HP 35S, I recently sold mine for twice what I paid for it because I don't like it and saw the sold prices on eBay. No regrets. Sorry if I'm driving the market prices up but it covered a fair chunk of the "spare" HP 15 CE that I'm sticking in the cupboard for the impending apocalypse, or something.

[Steve Simpkin]

(12-28-2023 12:41 AM)avsebastian Wrote:  

(12-22-2023 09:53 PM)bxparks Wrote:  A 50gii would be cool, but I hope the 35s (or something similar) is resurrected before that. It is unfortunate that the 2 RPN calculators approved for the FE exams are out of production. The prices for the 35s on eBay are out of control.

But.... The hp 15C is similar or superior to hp 35s, or not ,for that exam?

Maybe so, but it is not an approved calculator for the FE exam.
Calculators allowed on the FE exam

[Eddie W. Shore]

By the fact that we are still talking about RPN and we can apps and/or buy RPN calculators, RPN is still relevant.

[twoweims]

(12-28-2023 11:18 AM)Steve Simpkin Wrote:  Maybe so, but it is not an approved calculator for the FE exam.
Calculators allowed on the FE exam

My how times have changed...
I passed my EIT exam using two 15-Cs (An extra in case of catastrophic failure?).
But, that was many years ago...

[Raymond Del Tondo]

(12-24-2023 11:19 AM)Matt Agajanian Wrote:  On the lookout for a 33S and on the subject of the outrageous, here’s a doozy:
Now THIS is outrageous!!

That offer is insane IMHO. The seller won't find a buyer for that price.
The 32S may be one of the best RPN calcs,
and I like it very much for the clear interface and the big digits.
Actually I paid less than 50 Euros for a 32S from 1995 with the usual contact problem,
which can be resolved with some effort.

NB: Why would you want a 33S?
That machine has an awful keyboard layout and awful display similar to the 35S.

[Thomas Klemm]

(12-29-2023 02:47 AM)Raymond Del Tondo Wrote:  Actually I paid less than 50 Euros for a 32S from 1995

This makes it a rather expensive damaged box.

[Raymond Del Tondo]

(12-29-2023 12:57 PM)Thomas Klemm Wrote:  

(12-29-2023 02:47 AM)Raymond Del Tondo Wrote:  Actually I paid less than 50 Euros for a 32S from 1995

This makes it a rather expensive damaged box.

Since it's the usual zebra strip shrinking problem, it's repairable easily:-)