To me, not having to hit the home button, swipe, enter pin, find app, tap app, wait for an animation all before I can do anything the app is supposed to do, and then have to do most of that all over again if I don't touch it for a minute, is an excellent reason for a purpose-built device. Also, fucking buttons. I love buttons. Touch screens are awful.

I can't argue against the general purpose utility of a touchscreen, but I find touchscreens and the software we have built for them to be really cumbersome. For one, buttons on a calculator won't move on me at uncertain points during interaction! Doing things on smartphones is rarely succinct either as you illustrated.

But I also find excuses to put switches and dials on things and am the kind of person to think screen based aircraft cockpits are a regression.

I like touchscreen devices for infrequent input interactions. If my screen is already unlocked and the app I need is already open, for consumption based applications like article reading and video watching, it's great. But as soon as I get an on-screen keyboard, I end up frustrated very quickly.

The article links to this explanation of RPN and its benefits. https://www.swissmicros.com/what_is_rpn.php

After reading, I discovered the macOS calculator supports RPN (Cmd+R) and it is about as cool as described. Looks like the iPhone calculator does not but I'm sure there are great apps.

The firmware for the DM42 is based on GPL'd software available for all major operating systems (including iOS.)

http://thomasokken.com/free42/

For iPhone, PCalc [1] is quite good. It's also excellent on iPad. In fact, when my iPad 3 was due for replacement, PCalc almost persuaded me to go with iPad Pro instead of switching to a Surface Pro 4, but the SP4 won for better web browsing, better copy/paste, and OneNote.

The MacOS calculator's RPN mode is annoying. They don't get stack lifting right.

Suppose you want to compute sqrt(12) + pi.

Starting from an empty stack, this will do it on an HP calcualtor, PCalc, both RPN calculators I downloaded from the Windows Store, and, well, pretty much every RPN calculator I've used except from Apple:

  1 2 SQRT Pi +

When you hit the Pi key, it pushes Pi onto the stack, lifting up the sqrt(12) that is already there.

On the MacOS calculator, the Pi overwrites the sqrt(12).

If you do it this way:

  1 2 SQRT 3 . 1 4 1 6 +

then it works the same everywhere.

One other difference to watch out for. On some calculators, this:

  2 ENTER +

will give 4. This includes some HP calculators, such as the HP-15C. On these calculators the ENTER pushes whatever is in X, and leaves a copy in X with a flag set telling it that if you enter more digits they should overwrite X. Number entry goes directly into X, so the "2" goes into X, the ENTER pushes X to Y, so now X = 2 and Y = 2. So "+" works, giving 4.

On others, it will give a missing operand error. This includes the HP-48 family. On these calculators, number entry does not take place in X. It takes place in some sort of input buffer, and ENTER pushes that onto the stack so it ends up in X. So the "2" goes into the input buffer, ENTER signifies you've finished and 2 goes to X. X was empty before so nothing gets pushed to Y. So you've only got one operand and the "+" fails. (On these calculators, operators other than ENTER implicitly insert an ENTER first if the input buffer is not empty).

I'm not sure why HP changed this. The older calculators only had 4 stack positions, no entry buffer, and the display only showed X. By the time of the HP-48 they had many many more stack positions, an entry buffer, and the display could show the bottom 4 stack positions (or the bottom 3 and the entry buffer during digit entry). Perhaps the HP-48 behavior is what they always wanted, but decided it would be too confusing on the older calculators where your visibility was limited.

PCalc and MacOS calculator are like the HP-15C. PCalc has an "HP 48 Style" option on the advanced settings page if you prefer the HP-48 behavior.

[1] http://www.pcalc.com/

From the DM website: Compact size - are small enough to easily fit in any shirt pocket or purse or school backpack Extended battery life - have low power requirements, a single CR2032 will last for many years Full-sized capabilities - have all of the mathematical functions and programming power of full-sized HP calculators Connectivity - have an USB connection to save and load the complete state of the calculator including all programs and registers Firmware update - can be updated to the latest firmware release through the miniUSB connection Nostalgia - give you the feeling you had decades ago

To be fair, for this dev the reason it is better is it makes them happy.

I'm similar. I have my HP 49G sitting on the desk near me. Don't use it much, which makes me sad.

I have several things I like more about RPN. Especially over infix, it is a bit easier for me to decompose what I'm doing. Especially since I can't stand the arrow keys to jump around the bloody equation as I'm entering it. That said, I don't think it is "de facto" superior. I do like it, though.

> Explain why RPN is so much better than infix.

At least in my experience, it allows easier reuse of previous values. This makes RPN based calculators easier to use for exploratory kinds of work.

On my PC desktop I use an RPN calculator, I find it so much more useful than a standard style calculator. I think it's because you can see the stack and visually validate the numbers you are working on.

I use RPN Calculator v1.3 by Bill Menees, I find the interface a lot cleaner that the others I've tried.