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 analysis course amazed that it could even solve those equations (which I’m sure the TIs could do as well).
With the GX (which I got, and it still works) you could run metakernel [0], which itself was one heck of an upgrade over the base system and really an unbelievably impressive effort in its own right. It pushed the hardware so much farther it's still stunning. The HP48 remains one of my favorite calculation devices ever, with a great ratio of utility for both the most simple brainstorming calculations and going right into great depth. I'm still bummed my favorite emulator for iOS devices (m48+) stopped getting updates and faded away, and also that HP let its calculator division languish. What a tool.
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.
One difference is you see all intermediate results. That's huge for avoiding mistakes. In-fix, if you type (5+5)*(9+9), you only see the end result. Post-fix 5 5 + 9 9 + *, you see 10 and 18 along the way.
Another is the stack lets you easily reuse subresults. If you've computed the total energy and want to use it three places, you pick it off of the stack. All your work is there. It's very common that this happens.
It's an incredible productivity boost once you get used to it.
It gets even better when you tag numbers with the correct units. The calculator does type checking and automatic unit conversions. So if you key in the wrong operations, you'll either get an error somewhere along the way (from eg. trying to add something in m/s to something in m/2^2) or you'll notice the units at the end of the calculation don't match what you're supposed to end up with.
For general purpose programming, I want to write expressions in algebraic format but for interacting with a calculator RPN is easier. It removes a whole layer of abstraction wondering what the machine is doing.
I would imagine if I were young today and started with a modern multi line calculator with textbook display then that is what I would be comfortable with but for folks born before 1980 or so the algebraic calculators of our time were error prone.
I have an HP 27S that is algebraic and breaks the mold of being error prone because it shows the whole expression up until the point where a part can be evaluated. Then it evaluates the inner part while still showing the rest of the expression.
> Not sure why I'd want this: (flags & (4 == 4)), but that's what flags & 4 == 4 does.
Originally there was no && operator. You had to use & for Boolean conjunction too. The precedence makes sense under that condition. (And later couldn't be changed without breaking existing code.)
We had plug-and-chug competitions at school: big equations with some inputs, ready, go. The HP RPN folks would always beat the algebraic (casio, TI, etc) ones.
I bought an HP48 in 1990 junior year in college when it came out. A calculator WAS required for engineering school, but this one made everything way easier. I think it was almost $200. Anyway, once you go RPN, you don't go back. It makes way more sense. It finally died 5 years ago: the keys stopped working. I read about how to repair the keypad but finally had to let go. I had all my crib sheets from engineering school stuffed into the pouch. That calculator was epic. I can't imagine trying to do complex math with a slide rule, even though that's how engineers had done it for ages.
Similar story. Got a 48GX in high school. Everyone had TI89, maybe TI-92. I was the only one with HP.
Even with its lowly Saturn CPU and perceptually slower, it was trouncing the TIs at basically every task, especially when you customised it.
I learned RPN and RPL alright, but also got to dive into System RPL: the low level, faster, much more rich RPL, but where every argument was basically unchecked as it was more like HP-provided ASM routines in disguise.
And then learned to bit-bang stuff on the screen in assembly with all the timing tricks to produce 4 grayscale instead of just black/white. Great for coding small games.
Got the the third party CAS algebra extension card that also replaced the original UI for the same thing, only faster and better, and with a much more potent symbolic solver, whose UI was absolutely glorious to write, select, navigate, and perform advanced stuff.
Also got a maxed out storage expansion for the second slot. Such storage was not solid state so it required a continuously operating CR2032 battery to persist over time.
Unfortunately, as robust as it was, some time after engineering school it took a hard fall too much and was irreparably broken.
Later got my hand on a HP49G+, ARM powered but surprisingly the default was to run an emulation of the Saturn CPU, and CAS was bundled. You could still code for the ARM one though. By that time I lost interest so it currently sits in a drawer. Also preferred the 48 boxy design, especially the mushy keys of the new one were way worse.
I took an exam many years ago that required a non-programmable calculator; I told the instructor I literally had no idea how to use a non-RPN calculator any more and she was fine with me using my HP-15.
Sadly my collection of HP and other RPN calculators (there are a few) was stolen two years ago.
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.
With RPN you can just type facts in as you think of them, and figure out how to combine them later. With conventional entry, you have to have the entire equation in mind from the beginning, or backtrack to add brackets.
RPN has no use for brackets, because there is never any ambiguity.
Yep, had my Radio Shack calculator stolen from a college lab in 1990. Replaced it with a 32sii. After 30 years of RPN, I can never use a normal calculator. They are horrible.
