paxys 10d
What's interesting is that saving the results of a previous operation to memory and recalling/clearing them (M/MR/MC buttons) has been standard in calculators since the very beginning. It just has the most non-obvious user experience in the world so most people don't even know about the feature.
apike 10d
> For example, if a user calculates "89 x 15 = 1335" on one calculator and taps the arrow key, the result "1335" will be displayed on the other calculator, allowing the user to continue a problem while the previous equations are still shown on the screen. This makes it easy to notice errors.

While the UI is very different, the key benefit described here reminds me a lot of Soulver:

I love Soulver for how quickly it lets you throw together quick guesstimates and sanity checks. The ability to incorporate previous results by reference and update those on the fly greatly improves the clarity and my confidence in my experience.

tobr 10d
What a wonderful kludge. People can’t imagine that they would be able to go back and edit, or even see, the history of their calculations, so putting two calculators side by side seems like a brilliant idea.

It’s like if a new word processor consisted of two faithfully recreated typewriters, with a special button to send the most recently typed word back and forth between them.

furyofantares 10d
This seems pretty smart to me.

I think it's being dumped on because it's a "dumb" solution to something that is a non-problem for all of us here, which is probably why I've never seen this solution before. None of us would think of it.

But I think it's true that while most everyone knows how to use the most basic functions of a calculator, most people don't get any further than that, and this allows them to.

mikewarot 10d
This UI has a better impedance match to the way he, and many people who used desk calculators, think. It's quite elegant.
gkfasdfasdf 10d
Neat feature, IIRC Apple does not have a default calculator app because they can't make one that sets it apart from other apps as is the 'Apple way'. Maybe they should just adopt this one.
PaulHoule 10d
"The number of downloads grew at a sluggish pace at first because the app was designed so that just one calculator is displayed on the smartphone's vertical screen mode, while two are shown only when the screen is rotated on its side. So, many users only thought it was a regular calculator."
ape4 10d
I first thought it was going to show results in hex and decimal at the same time.
syntheticnature 10d
"If I had asked people what they wanted, they would have said faster horses." -- attributed, apparently wrongly, to Henry Ford.

Those of us who know RPN and other options are likely to squirm at this app, but in this case the "faster horse" approach seems to be easy for people to pick up and understand.

dm319 10d
Some similarities with RPN, except instead of two calculators working on two registers side by side, it's one calculator working on the bottom of several registers.

Both allow you to do complex interim calculations that can be hard to plan out on algebraic alone.

quartz 10d
The best feature on the Mac's built in calculator is the paper tape (⌘+t) which I stumbled on ages ago while accidentally having the calculator open and trying to open a new tab in my browser.

I always leave it open now and it has saved me countless times. Really with the iOS version had this feature built in as well.

dpb1 10d
Some of the strong points of this calculator is the main thing I use in RPN calculators with stacks. It's so helpful for me to duplicate a value and then operate on that, and be able to throw it away if I mess up, sanity check from where I started at intermediate calculations, etc. it's not identical, but many points others are mentioning in this thread are what I value from an RPN stack based calculator.

BTW, for anyone who is comfortable with RPNs, MacOS added the mode to their built-in calculator recently-ish. it's not terrible either. I've switched to it for my default experience. (even though nothing beats the HP 48g, as it's what I'm the most familiar with).

Also, on the article, really cool that someone added this on mobile. I love hearing about devs developing something that fills a niche and does so well. I feel like I'm out of ideas most days. Good for her!

asimpletune 10d
Improving upon the design of a calculator app is incredibly difficult. And before people complain that it's not improved, yes it is. For most people, this is way better. Congrats to him, he's living the dream. Building software that does a job, and then getting paid for that software. I just hope he doesn't suffer too many copycat apps.
5fOleL5Eo2So8qi 10d
The hard part of writing a calculator app is not parsing `0.1` versus `.1`. That's trivial. The hard part of writing a calculator app is getting precise answers instead of floating-point answers, and given that he thinks the hard part is parsing `.1`, it probably gets it wrong.
jhallenworld 10d
My daughter is struggling with this problem: on TI-84s, "(-) 3 x^2 Enter" gives -9. Personally, I think that if you have a dedicated negation operator it should have a higher precedence than power, but at the very least the calculator could highlight what it's doing.

"Hypercalc" the Android app does it, but TI-84 is the standard..

wishfish 10d
That's a brilliant & simple idea. I love it. Makes me wonder if anyone's made a small screen spreadsheet? Seems like that would be the obvious next step.

Something like a default of 3x4 or 4x4 cells. Would have most of the basic spreadsheet functionality, and maybe simple graphs to show comparisons. Interface designed for touch on a six inch screen.

xxr 10d
I haven't used this app, but something that makes me smile is that the paid version is only 563KB (the paid version is 4.6MB, and I suppose it's pleasant that the ad SDKs are "only" 4 megs). After seeing every major app take up 100MB+ for years, I had just assumed that there was some kind of static packaging inherent to all iOS apps that jacked the deliverable size up so high. I don't know whether Ueda was deliberately trying to get it as small as possible, or if his design is so elegant that it just naturally led to such a tiny artifact. Either way, as long as the 3.5" floppy is still in its sunset period[0], I suppose it's nice that there's modern software that will still fit on it.


qwezxcrty 10d
I don't see how this works better than any scientific calculator that shows history. Also don't understand why he put two sets of keyboards, to me it just doesn't make sense.

Marginally related: if you are looking for a non-sucking calculator app on desktop or mobile, try an emulator of a (modern or retro, at your choice) HP or TI graphical calculator. My personal favorite is the emulator of HP Prime.

icedistilled 10d
Why don't calculator apps at the very least display the current calculation like the casio FX-95? The current options of basic or scientific for mac/ios would be 100x better. The ticker tape only partially solves it.

FX 95:

supernova87a 10d
> ...Ueda recalled, "I thought it'd be easy, but it was unexpectedly hard." ... For example, while there are users who input 0.5 by tapping "0," the decimal point, and then "5," there are also users who only input the decimal point and "5," while omitting the "0." He said, "There were around 100 types of these sort of conditions, and it was a lot of work to solve them."

I wonder what other kinds of non-trivial calculator behaviors he had to rediscover from scratch?

chongli 10d
It’s interesting but the duplicate sets of buttons are a big waste of space. My favourite free calculator app is Desmos Scientific (by the makers of the graphing calculator) [1]. This app gives you as many entry lines as you like and they all remain live. You can also define variables and functions in one line and use them in another. In effect, it’s like a single column from a spreadsheet.


gfodor 10d
If you liked this app, stay tuned - I am working on a 3-calculator app that increases the utility of this app by up to 50%.
DangitBobby 10d
I love this! Also, today I learned that you can scroll through your history in the built-in android calculator by swiping down on the number input field!
WiSaGaN 10d
This is the innovation that everybody would see how obvious it is once it's out. And yet no one thought about making it for a very long time.
mrb 10d
As a quick calculator, I absolutely love the python repl/console. On my laptop I hit Ctrl-T python ENTER. It opens a terminal and I start typing 48*152 ENTER and I see the result. The history of calculations is saved. I can access previous calculations, edit one number and recompute. I see the last 100 lines or so, on one screen. This beats by far the convenience of this 2-in-1 calculator. I would KILL to have a good python repl on Android. However the only one somewhat usable is "Pyonic Python 3 interpreter" but it's clumsy to use as a calculator because it uses the standard alphabetic keyboard so you have to keep switching to the special characters layout to type math operators (-+/...) If this ONE detail would be fixed, and with some minor UI polish I believe it could become more popular than the 2-in-1 calculator...
noobermin 10d
I think this is why I prefer using the python idle as a calculator. You can assign an expression to a variable, but you can always scan up (assuming your terminal window is tall enough) to see what expression you used to calculate it. People are saying how this is the point of memory on calculators but once you save to M you basically need to remember what's in there. Seeing what you did to calculate whatever is better.

In a way then, the python idle is like this but with many calculators side by side.

chacha21 9d
An opportunity to post again my thoughts about software calculators !

hnjst 9d
I'm still completely baffled that we nowadays almost all have in our pocket a device able to run something like
ycombinete 9d
Just bought this for my iPad, which apple inexplicably doesn’t bundle with their calculator app.
tempodox 9d
This is such a nice example of how relatively simple ideas can still be of huge utility.
runeks 5d
> For example, while there are users who input 0.5 by tapping "0," the decimal point, and then "5," there are also users who only input the decimal point and "5," while omitting the "0."

The practice of including punctuation inside the quote makes this a somewhat confusing sentence, at least if you’re used to using a comma instead of a period for the decimal point.