What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999) • Hacker News Board

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#81

Post by SAI_Peregrinus » Sun, Mar 07, 2021, 12:37 AM UTC

mtalantikite wrote: post #37

aseerdbnarng wrote: post #13

I was forced to use an HP12C as part of my university degree. Once you get used to RPN it’s quite uncomfortable to switch back. It’s a much more intuitive way to do math once you get over the small hurdle. 15 years later and I’m still using the same calculator!

For whatever reason my high school had HP48s for my junior year math class, which got replaced the following year for TIs since “that’s what you’ll be using in college”. I much preferred the RPN and ended up convincing my parents my life would be easier with a new HP49g (which wasn’t a lie, it was). That thing helped get me through my math major and I’ll always remember my old school professor who taught my complex a…

I never used an HP, but I did have a TI-89, and used a program for it that added RPN input.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#82

Post by userbinator » Sun, Mar 07, 2021, 12:42 AM UTC

Another advantage to RPN is consistency between machines. Early algebraic models had differing limits of the complexity of the expressions they could evaluate.

Even RPN has a limit, that being the stack depth --- while most of HP's calculators had 4, the HP48 has one limited only by available memory.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#83

Post by ryebit » Sun, Mar 07, 2021, 12:57 AM UTC

I've had the Droid48 app on my android phone for years. It's a little unstable, hope author updates it. But it's so awesome to have a 48GX available whenever, while my real one sits safely on the shelf at home.

When I first got that thing as kid, nearly returned it, RPN seemed so bizarre. So glad I didn't... Really love that language, would never have understood stack based VMs as deeply if it weren't for the things I coded on that calculator.

Droid48 - https://play.google.com/store/apps/details?id=org.ab.x48&hl=...

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#84

Post by dehrmann » Sun, Mar 07, 2021, 1:11 AM UTC

macintux wrote: post #68

pcardoso wrote: post #39

When I was starting my degree (around 96) I went to the US for a week and bought a HP48Gx since they were cheaper there. This happened a few weeks after a Swiss jet crashed departing NY and the reasons were not known at the time so the airport staff was very suspicious. When they saw the calculator and tried to do a simple test calculation and failed, I struggled to explain how use it, since it was also so new to me.…

Reminds me of the story of someone who took a Linux laptop through security; they wanted to see it boot, but didn't recognize the command line and were suspicious. The owner set PS1 to resemble a DOS shell prompt and they were satisfied.

I remember flying with a bunch of hard drives out of SFO in 2002. I was a little worried security would get 9/11 worried about them. Maybe because it was SFO are are used to seeing tech people flying with odd stuff, they didn't care.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#85

Post by dehrmann » Sun, Mar 07, 2021, 1:17 AM UTC

aseerdbnarng wrote: post #13

I was forced to use an HP12C as part of my university degree. Once you get used to RPN it’s quite uncomfortable to switch back. It’s a much more intuitive way to do math once you get over the small hurdle. 15 years later and I’m still using the same calculator!

> It’s a much more intuitive way to do math

Is it? It's easier to code an evaluator, but I'm not convinced it's necessarily more intuitive. In practice, only addition/subtraction and multiplication/division are ambiguous. I'll also play devil's advocate and admit order of precedence is somewhat arbitrary, and precedence of bitwise and and equality is wrong in most languages. Not sure why I'd want this: (flags & (4 == 4)), but that's what flags & 4 == 4 does.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#86

Post by JoeDaDude » Sun, Mar 07, 2021, 1:58 AM UTC

The only reason I don't use my HP-15c scientific, which I got in college well before the turn of the century as an EE undergrad, is because it has been emulated on my phone. Well worth the price:

https://apps.apple.com/us/app/hp-15c-calculator/id503720774

And oh, BTW, I still have my 15c.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#87

Post by GilbertErik » Sun, Mar 07, 2021, 2:24 AM UTC

bitwize wrote: post #47

There's an open-source Android app called Droid48 that gives you a virtual HP48, if you're into that sort of thing. I know when I'm out with coworkers and they whip out Droid48 to calculate the tip, I picked a good place to work.

I've had a decent experience using RealCalc Plus, although it's just my backup when I don't have my 32SII handy.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#88

Post by Scott_Sanderson » Sun, Mar 07, 2021, 2:52 AM UTC

Picked up an HP calculator to take the FE exam. The other approved calculators were simple 4 functions calcs. I assumed everyone would be on the HP but I was the only one who had one at the testing center.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#89

Post by bsder » Sun, Mar 07, 2021, 2:53 AM UTC

machinelabo wrote: post #70

aseerdbnarng wrote: post #13

I was forced to use an HP12C as part of my university degree. Once you get used to RPN it’s quite uncomfortable to switch back. It’s a much more intuitive way to do math once you get over the small hurdle. 15 years later and I’m still using the same calculator!

I don’t think it’s more intuitive. It’s just that you’re used to it.

Everybody thinks that RPN is about the inverted order when it's really about having an explicit stack instead of an implicit one.

If you're using "algebraic", you sometimes have to put a "(" into your expression a long way ahead of when you need it. Think of how many times you have to go and fix up your left parens when writing C code conditionals. On a calculator, if you screw up, go back to start. Also, old calculators had parentheses limits.

"Modern" algebraic calculators mitigate this somewhat because they can enter the expression in text form on a dot matrix LCD so you can go back and add/delete parentheses as required.

An explicit stack means that I can start and stop subexpression calculations at various points and cache the results. It also means that I can rearrange precedence at my convenience--of course, the flip side is that precedence is my problem instead of the calculator's.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#90

Post by lozaning » Sun, Mar 07, 2021, 2:53 AM UTC

dehrmann wrote: post #84

macintux wrote: post #68

Earlier quoted context omitted.

Reminds me of the story of someone who took a Linux laptop through security; they wanted to see it boot, but didn't recognize the command line and were suspicious. The owner set PS1 to resemble a DOS shell prompt and they were satisfied.

I remember flying with a bunch of hard drives out of SFO in 2002. I was a little worried security would get 9/11 worried about them. Maybe because it was SFO are are used to seeing tech people flying with odd stuff, they didn't care.

I worked in Mountain View and lived in Palm Springs for a while and used to commute back and forth through SFO/PSP.

Im convinced you could take damn near anything through SFO tech wise, cause they've seen it all. Meanwhile explaining to the TSA people in Palm Springs why I've got 3 laptops, let alone 4 dozen cell phones was always a hassle and a half.