EE Pros: Is RPN still relevant?

[amspire]

Back about 1979, we had our own Automated Test bench and I had to make and program fixtures to test 600 ohms telephone-type transformers. The computers were HP 9852A desktop caculators - 64K of ram that had to be shared between the Basic program and running the GPIB card, the RS232 card, the printer, the tape drive and the OS. The end result was that a program was typically a few hundred lines maximum, and variables were A to Z.

To handle all the different transformers, I had to write an interpreter that reads the test instructions from a file on the tape for the particular transformer and run it. The only possible way was to write a RPN interpreter because it is just so simple - is the next item in the file a number? If yes, put it on the stack. If it is a letter, it is a command that can pull numbers off the stack. That essentially is the whole interpreter and only takes about 15 minutes to write. In some cases, a command might put numbers back on the stack for the next command to use. No tokenising, no brackets.

So a test might be:

1 2 I
3 4 O
100 R
1000 F
50 V
49 51 M

which means turn on relays 1 and 2 to connect a winding to the source, turn on relays 3 and 4 to connect the output to the dvm, set the dvm to the 100V AC range, set the source to 1KHz at 50V. Then measure (switch on the source and measure output voltage. If it is between 49V and 51V it passes. Using the RPN order made the programming very simple. The thing is it is also simple for the brain. We often add a huge amount of hidden complexity to things necessarily, particularly now when computing speed and memory is no longer an issue.

If I need to use Trig, I often get the numbers first before I even think about which trig function I need. So I calculate the voltage and phase angle first, and once they are on the stack, I will only start to think about "do I need sin() or cos()"?

[djacobow]

I searched all drawers...  could only find RPN 



34S is the one always on my desk

Is that 34S the WP34S? The one made from a hacked HP30b?

I have one of those and it is awesome. The very idea of it is awesome.

[eugenenine]

Mine has sat loved for a while so I decided a couple months ago to pull out and give it some love.  USB to serial and an adapter since I couldn't find the old one


And I can transfer files again.

[helius]

There are user-contributed programs that replace the default stack view for the HP48: they are faster and better looking. Also math packages that make it a much more powerful tool. http://www.hpcalc.org

[eugenenine]

I've been downloading a lot from there lately.  I've seen some of the stack replacements.  I'm running into memory issues now, but can't find a ram card under $100 on ebay or amazon.  I see all the specs for the cards were published, I may have to see if I can design one in kicad.

[xrunner]

I was browsing Ebay and just for the fun of it searched for the HP 42S (which I still have). They are going for over $200! But I'm not selling mine. 

[jakeisprobably]

I was browsing Ebay and just for the fun of it searched for the HP 42S (which I still have). They are going for over $200!

  ...thus the real reason for starting this thread... I saw how much people were selling RPN calculators for on eBay and figured I was missing something here.... Too many YT cool kids are playing with them. I wanted to know why. This thread is awesome. Thanks

[kultakala]

Is that 34S the WP34S? The one made from a hacked HP30b?

I have one of those and it is awesome. The very idea of it is awesome.

Yes, it is the WP34S!
I bought it complete...  and it is really good.

[CJay]

I'm not an evangelist.  I use RPN and have for over 40 years.  Use it if you think it helps, skip it if you don't.

Absolutely that ^^^^^^^^^^

Use the tools that get the job done properly in the way that works best for you, I wish people would stress it more often instead of evangelising their favoured choice, after all it's exactly what they're doing.

By all means learn RPN but don't feel bad if it doesn't work for you and don't hesitate to try and find a way that's better for you. 

[Vtile]

It worked to me, I got through most of my education with end of the nineties TI graphing calc (closer to 80 than 90 as a model number). Then when I reseated myself to school I decided to go with CAS and everything, got RPN machine. I actually feel like  not to had one before as it just fits to my head and makes the boring mindnullifying math a interesting once again.

People love it or hate it. There is only one way to find out which group of people you belong.

PS. HP35s have trig inaccuracy bug, so if you need high precision trigs you need to get a community written trig package for it (google is your friend).

[MrAl]

Hi,

I see that in most of this thread that RPN is being taken as some sort of physical calculator with buttons and the like, but RPN is not just a kind of calculator, it's a way of evaluating expressions and this means it has wider application than in just an RPN calculator.

For example, most Infix calculators probably use RPN internally, because that's the best way to evaluate expressions, for a machine.  In human terms, Infix is more widely used but once entered into a device the chances are that sooner or later it will be converted into an RBN string because that is easier for a machine to understand.  There's much less logic to doing an expression with RPN than with Infix where you could have 100 parentheses waiting around for that last one to be able to finish the calculation.

I've used both low end HP's and high end HP's and low end TI's and high end TI's and i can tell you that for a calculator the least important thing is whether or not it does RPN or not.  The most important thing is what kind of apps you can use with it.  If you work in a certain field and you cant get an app for something you need to calculate, you want want that calculator.  This means that ultimately the best 'calculator' choice is not a calculator at all but a laptop.  If you just want to bang around with it then it doesnt matter as much, but for your main work you'll get what you need.

Back in the old days when i first discovered the TI high end calc's i loved them, and they did all kinds of stuff.  Then i met the advanced HP that did Fourier and Laplace Transforms, then i went back to the TI when it came with even more advanced functions.  They are all on the sidelines now, now that i have software for the PC that i wrote myself and also some that i downloaded, and none of those advanced calculators, even all taken together, can even come close to what i have on the computer these days.

[David Hess]

They are all on the sidelines now, now that i have software for the PC that i wrote myself and also some that i downloaded, and none of those advanced calculators, even all taken together, can even come close to what i have on the computer these days.

I use Mathematica but in parallel with my RPN HP50g.  A computer and even PDA lacks the convenience of a dedicated calculator when I am designing on paper.  The calculator is portable, I don't have to worry about the batteries dying, and it has a superior user interface unless something much more complex is being done and not even then sometimes.  Oddly enough it is often faster as well although the 48 MHz ARM based HP50g is slower than the 4 MHz 4-bit HP48g that it replaced.

It looks to me like HP is leaving the calculator business so I suspect RPN as used as a calculator interface will finally succumb.

[eugenenine]

I was browsing Ebay and just for the fun of it searched for the HP 42S (which I still have). They are going for over $200!

  ...thus the real reason for starting this thread... I saw how much people were selling RPN calculators for on eBay and figured I was missing something here.... Too many YT cool kids are playing with them. I wanted to know why. This thread is awesome. Thanks

Most anything retro si in now.  Do a search for Commodore or Amiga or even Atari and you'll see the same high prices.

[eugenenine]

They are all on the sidelines now, now that i have software for the PC that i wrote myself and also some that i downloaded, and none of those advanced calculators, even all taken together, can even come close to what i have on the computer these days.

When we all used calculators you couldn't fit a computer in your pocket.  One of my early projects was making a data acquisition board for my 48sx.  I gave up on that project after a while when you were able to buy DMM's, DSO's etc that could communicate with a PC/laptop.

When I learned that forth was postfix I started looking into it, before I wasn't interested as I though it just another language.

Now a days I don't use my hp as much as I would like but the feel of the keyboard is still there.  Its like asking someone why they have a manual transmission.

In reality its probably not relevant much anymore, I still prefer to design my wooddorking  or schematics on paper, never got used to cad either.

[rstofer]

Back in the old days when i first discovered the TI high end calc's i loved them, and they did all kinds of stuff.  Then i met the advanced HP that did Fourier and Laplace Transforms, then i went back to the TI when it came with even more advanced functions.  They are all on the sidelines now, now that i have software for the PC that i wrote myself and also some that i downloaded, and none of those advanced calculators, even all taken together, can even come close to what i have on the computer these days.

For the last month, I have been playing with wxMaxima on a PC and it is terrific!  No calculator will ever compare to this CAS (Computer Algebra System) with a 27" screen.  About this, I am an evangelist!  I believe!

Not all that many people actually need a CAS in their everyday lives.  Those who work in tech probably do but they are probably already using such a thing.  Everybody in a college STEM program needs something.  I just use the calculators for grunt number crunching.

Maple and Octave are also highly regarded as CAS programs.  Maple tends to cost money and, although I have downloaded Octave, I haven't started using it.  I'm still learning about wxMaxima.  Matlab needs to be on the list as well.  Mathworks has libraries for everything!

[eugenenine]

For the last month, I have been playing with wxMaxima on a PC and it is terrific!  No calculator will ever compare to this CAS (Computer Algebra System) with a 27" screen.  About this, I am an evangelist!  I believe!

Not all that many people actually need a CAS in their everyday lives.  Those who work in tech probably do but they are probably already using such a thing.  Everybody in a college STEM program needs something.  I just use the calculators for grunt number crunching.

I grabbed the slackbuilds for this the other day, I just need to find a good tutorial on getting started

[rstofer]

For the last month, I have been playing with wxMaxima on a PC and it is terrific!  No calculator will ever compare to this CAS (Computer Algebra System) with a 27" screen.  About this, I am an evangelist!  I believe!

Not all that many people actually need a CAS in their everyday lives.  Those who work in tech probably do but they are probably already using such a thing.  Everybody in a college STEM program needs something.  I just use the calculators for grunt number crunching.

I grabbed the slackbuilds for this the other day, I just need to find a good tutorial on getting started

If you are asking about wxMaxima, there are two great books that have terrific examples specifically related to wxMaxima for Calculus.  It's simple enough to just take the ideas and put them to use in other areas.

https://wxmaximafor.wordpress.com/

The User Manual is online but it doesn't seem terribly approachable.  It is great as a reference, not so much as  a tutorial.

I have attached the code for a "Ball Thrown In Air" physics problem.  The gravitational constant shows clearly that the experiment wasn't done on Earth.  The two graphs are included.  If you want, just retype the code and see how it works out.  I get most of my education by copying.

It is worth noting that the entire problem is contained in lines 2..6.  Everything else is just gilding a lily.
Line 2 defines the gravitational constant
Line 3 defines the initial velocity
Line 4 describes the standard equation for motion: H(t)=V₀t+1/2at²
Line 5 takes the derivative of the function in Line 4 to get v(t), the velocity as a function of time.  Note that wxMaxima does the derivative, I didn't have to provide it.
Line 6 finds the time when the ball impacts the ground by looking for the second root (away from 0) for the H(t) equation.  In other words, where H(t) = 0 with t <> 0.

That's it!

[frozenfrogz]

OT: I love how these threads always have a tendency to end up deep in nerd territory 

Please go on!

[bitseeker]

I used to get magazines from the library with ads for hp calculators, it was like playboys for nerds.
I graduated high school and then 48sx was released and I worked and saved months for it and finally saved up the $300 and bought it from a store called service merchandise.  It was under glass like in a jewelry store so I made my purchase then went to the waiting room where the product you bought came out on a belt like luggage in the airport.  I almost cried when that little box finally came down the belt for me.

Holy smokes, that might've been where I bought my 28S back in the day. Been using RPN ever since, even for simple calculations. As someone else posted, Free42 works a treat. Or if you want the HP look, Droid48.

I haven't used my 28S in ages. Perhaps I'll hunt down some N-size NiMH rechargeable batteries (it uses three cells).

[Vtile]

I was browsing Ebay and just for the fun of it searched for the HP 42S (which I still have). They are going for over $200!

  ...thus the real reason for starting this thread... I saw how much people were selling RPN calculators for on eBay and figured I was missing something here.... Too many YT cool kids are playing with them. I wanted to know why. This thread is awesome. Thanks

Most anything retro si in now.  Do a search for Commodore or Amiga or even Atari and you'll see the same high prices.

Vintage Casios run for $1 a piece. 

[bitseeker]

I was browsing Ebay and just for the fun of it searched for the HP 42S (which I still have). They are going for over $200! But I'm not selling mine. 

I'm not selling my HP calculator either. That would be anti-TEA and my other HP gear wouldn't be too happy about it.

[eugenenine]

For the last month, I have been playing with wxMaxima on a PC and it is terrific!  No calculator will ever compare to this CAS (Computer Algebra System) with a 27" screen.  About this, I am an evangelist!  I believe!

Not all that many people actually need a CAS in their everyday lives.  Those who work in tech probably do but they are probably already using such a thing.  Everybody in a college STEM program needs something.  I just use the calculators for grunt number crunching.

I grabbed the slackbuilds for this the other day, I just need to find a good tutorial on getting started

If you are asking about wxMaxima, there are two great books that have terrific examples specifically related to wxMaxima for Calculus.  It's simple enough to just take the ideas and put them to use in other areas.

https://wxmaximafor.wordpress.com/

The User Manual is online but it doesn't seem terribly approachable.  It is great as a reference, not so much as  a tutorial.

I have attached the code for a "Ball Thrown In Air" physics problem.  The gravitational constant shows clearly that the experiment wasn't done on Earth.  The two graphs are included.  If you want, just retype the code and see how it works out.  I get most of my education by copying.

It is worth noting that the entire problem is contained in lines 2..6.  Everything else is just gilding a lily.
Line 2 defines the gravitational constant
Line 3 defines the initial velocity
Line 4 describes the standard equation for motion: H(t)=V₀t+1/2at²
Line 5 takes the derivative of the function in Line 4 to get v(t), the velocity as a function of time.  Note that wxMaxima does the derivative, I didn't have to provide it.
Line 6 finds the time when the ball impacts the ground by looking for the second root (away from 0) for the H(t) equation.  In other words, where H(t) = 0 with t <> 0.

That's it!

Yes, wxMaxima

But now I need to re-learn calc and / or physics, the old hdd is getting quite fragmented.

[eugenenine]

I used to get magazines from the library with ads for hp calculators, it was like playboys for nerds.
I graduated high school and then 48sx was released and I worked and saved months for it and finally saved up the $300 and bought it from a store called service merchandise.  It was under glass like in a jewelry store so I made my purchase then went to the waiting room where the product you bought came out on a belt like luggage in the airport.  I almost cried when that little box finally came down the belt for me.

Holy smokes, that might've been where I bought my 28S back in the day. Been using RPN ever since, even for simple calculations. As someone else posted, Free42 works a treat. Or if you want the HP look, Droid48.

I haven't used my 28S in ages. Perhaps I'll hunt down some N-size NiMH rechargeable batteries (it uses three cells).

I don't know how big of a chain they were.  I bought mine in Columbus Ohio, it was on Hamilton Road.

[bitseeker]

Service Merchandise seemed to be everywhere. I remember many fun times watching for my purchase to rumble down the conveyor.

NiMH N-type (aka LR-1) batteries seem to be hard to find in the US. So far, I'm only locating sources in the UK.

[eugenenine]

N size NIMH?  Amazon, battery junction, etc all have them.