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!
On that note, I always end up using an HP 48g emulator on my phone as my main calculator app. I've been using Droid48 for many years now [0]. I'd initially looked at most of the native mobile calculator apps before realizing that since I was comparing them all with the HP 48 experience, I might as well just use an emulated HP 48 and be done with it.
On a laptop or desktop, though, I've come to use Emacs Calc [1] pretty heavily. There's a surprising amount of power in it. It's pretty cool to be able to do things like operate on matrices of symbolic expressions via a stack interface.
I was thinking the same thing while reading the article. I have been using RPN calculators for 40 years, and it has become second nature to manipulate the stack to have two calculations going at the same time, and then merging them, if needed.
For the HP48/50 fans here: try the HP Prime. The color display is amazing. It requires some relearning because the UI is different, but it still has full-featured RPN mode. The keys are good, too--it looks and feels like a proper HP calculator. I used a 48SX in college and 50G later, but the Prime is the one to have now. (It's also the one my daughter steals now that she's in more advanced math and science classes.)
What I want is a phone app calculator that works like the Python REPL/console. Save ALL previous calculations. Display the last dozen or so. Can scroll through them. Tap on one to recall it, edit one number, recompute. Done.
This would beat by far the convenience and usability of this 2-in-1 calculator. I would KILL to have this.
In fact, on my laptop, I use the Python REPL as a calculator. 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.
The only one somewhat usable Python REPL on Android 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...
I've been using an app called Calctape[0] for years that sounds similar to what you're describing.
It's essentially a 4-function calculator that records every step on tape, but you can edit any digit anywhere and all related steps are immediately recalculated, like on a spreadsheet.
Interesting. Not exactly what I described though (sorry I did not explain very well.) What I meant, you type 2 calculations:
> 1+1
2
> 10+10
20
Then if you tap the first line ("1+1") my ideal REPL would add it to the bottom:
> 1+1
2
> 10+10
20
> 1+1_ (with the cursor here ready to edit it)
Then you can for examlpe change a 1 to 2, then type ENTER:
> 1+1
2
> 10+10
20
> 1+2
3
That way you can easily compute a few things, then compare both the expressions and results of the last few calculations, and quickly make edits/corrections as needed.
Very cool ! For units conversion I use GNU Units. But qalc seems to combine the benefits of both the Python REPL and GNU Units. I just tried the command-line version and noticed it doesn't support recalling the history (UP arrow) and editing calculations. This is unfortunately a deal-breaker :-( Don't have time to submit a patch.
If you know an APL-like or are willing to learn enough to use as a calculator (there are unfortunately some uncommon things like % being division), there's J on iOS: https://apps.apple.com/us/app/j901/id1483497239. There ought to be a way to get it on Android.
I have an older version of it and it works fine although the keyboard is a little clunky. However, you need to swipe to get to previous computations. I'm not sure if they changed that in the new version.
The built-in calc sucks: when the keyboard is displayed to edit the current expression, the app can only display ONE previous expression at a time. Sometimes I calculate things and need to refer to 2 or more previous results. I would have to copy paste them one at a time (cumbersome) or memorize them.
If only it could display about a dozen previous results while the keyboard is active... With a Python REPL I can just assign intermediate results to variables.
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.
a calculator with a history being superior was my first thought too. there are advantages to this approach too, however. The history is selective, so if you make a mistake/typo, that isn't now permanently in your history as a footgun to go back to and re-make. here you have two states and you have full control over them.
of course you could also just have a history where you can delete individual items, but this also makes the interface more complicated and might not be as intuitive (and requires more discipline)
The issue is that the default Calc doesn’t let you see history and nearly every single 3rd party calc doesn’t follow iOS design principles, just doesn’t look very good, and are often inexplicably slow.
> 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.
There's a lot of diff tools that essentially do exactly this.
Indeed, this is, like, a solved problem on every other platform! Apple instead designs their apps after tech from the 80s[1] and is now stuck there for life.
Indeed, it's a solved problem on iOS too! This story isn't about someone releasing a new app into a desolate marketplace without any calculator apps (and hey, turn that iOS default calculator sideways for some fun), it's a human interest story about someone releasing a new app into an already-crowded market with a slightly new twist, and finding success there.
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.
This article made me realise why I use a python shell over a calculator app. It's nice to refer back to my previous computations and results. Several people here mention RPN; I work in tech, definitely understand stacks and get that I would be able to view my previous computations. Yet it's not something I took the time to discover, there were always other ways.
I've always believed that there is still a lot of low-hanging fruit left in crafting user friendly experiences for consumer facing applications. Who would have guessed this would be the case even in the design space of something as fundamental as calculators! ~20k paid users seems surprisingly large. But I'm not plugged into the app dev scene, so perhaps this isn't unusual.
> I just hope he doesn't suffer too many copycat apps.
There were 2k clones of flappy bird within a month of its release. By now there must be at least a dozen programmers copying this idea (Twin-Calc) for other platforms, myself included.
"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.
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.
> there was some kind of static packaging inherent to all iOS apps
There was for apps using Swift. Before the Swift ABI was frozen, iOS apps using Swift had to statically link the Swift standard library. Nowadays, iOS provides it as a dynamic library.
I mean... it depends what you want to support. My web calculator [fully client side] is 370kb of JS. It has features that this doesn't have (3d rendering, solving equations), but doesn't have code that this needs (mostly, the keyboard)...
On the one hand, there's your claim that a web version of TwinCalc should be 56.3K or so. On the other hand, there's a world of existing web apps which are generally very much larger than that.
A smaller footprint than 563K would be a dubious advantage for web apps in either case.
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.
I've always wanted a browser extension (or similar) that opens a small 10x10 spreadsheet so I can quickly do some calculations. For example, if you are shopping online and have various options that all have different shipping costs etc. It would be nice to do a quick breakdown of costs without having to open Excel.
It's a little surprising Google hasn't done this already. A small (maybe inline, maybe floating) popup that gives you a little grid. Would autosave to Sheets. That would be perfect.
Anyways, that's a great idea you have. I never knew I wanted this, but now I want it very badly.
Numbers runs on iOS—not terribly easy to use, per se, but absolutely gets the job done. There was a light version of Excel even on the BlackBerry-styled Windows Mobile phones that similarly was great for, oh, comparison pricing or converting multiple values other tiny math jobs.
One specifically designed for phones with a very limited feature set, though? That could be very handy.
I occasionally fire up Numbers on my i-devices. It's ok on iPads. But on my iPhone it's a bit painful. Haven't tried it on there in a few years. I should try it again to see if works better on the small screen now.
I find it to be very japanese. elegance expressed in such a simple form. blindingly obvious ... now. so hard to arrive at this design choice. i love this. it's poetic.
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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!
On a laptop or desktop, though, I've come to use Emacs Calc [1] pretty heavily. There's a surprising amount of power in it. It's pretty cool to be able to do things like operate on matrices of symbolic expressions via a stack interface.
[0] https://play.google.com/store/apps/details?id=org.ab.x48
[1] https://www.gnu.org/software/emacs/manual/html_mono/calc.htm...
https://play.google.com/store/apps/details?id=advanced.scien...
But it lacks the stack undo of the 48 emulators.
Deleted Comment
This would beat by far the convenience and usability of this 2-in-1 calculator. I would KILL to have this.
In fact, on my laptop, I use the Python REPL as a calculator. 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.
The only one somewhat usable Python REPL on Android 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...
- iOS: https://apps.apple.com/us/app/instant-calculator/id163232882... - Android: https://play.google.com/store/apps/details?id=com.adrianmeji...
It's essentially a 4-function calculator that records every step on tape, but you can edit any digit anywhere and all related steps are immediately recalculated, like on a spreadsheet.
[0] https://calctape.app/
I have an older version of it and it works fine although the keyboard is a little clunky. However, you need to swipe to get to previous computations. I'm not sure if they changed that in the new version.
If only it could display about a dozen previous results while the keyboard is active... With a Python REPL I can just assign intermediate results to variables.
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.
of course you could also just have a history where you can delete individual items, but this also makes the interface more complicated and might not be as intuitive (and requires more discipline)
There's a lot of diff tools that essentially do exactly this.
[1]: https://www.creativebloq.com/design/iconic-calculator-inspir...
I've always believed that there is still a lot of low-hanging fruit left in crafting user friendly experiences for consumer facing applications. Who would have guessed this would be the case even in the design space of something as fundamental as calculators! ~20k paid users seems surprisingly large. But I'm not plugged into the app dev scene, so perhaps this isn't unusual.
There were 2k clones of flappy bird within a month of its release. By now there must be at least a dozen programmers copying this idea (Twin-Calc) for other platforms, myself included.
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.
[0]https://www.bbc.com/news/world-asia-62749310
There was for apps using Swift. Before the Swift ABI was frozen, iOS apps using Swift had to statically link the Swift standard library. Nowadays, iOS provides it as a dynamic library.
(and having a stable ABI is quite an accomplishment for a language like Swift. See https://faultlore.com/blah/swift-abi/)
A smaller footprint than 563K would be a dubious advantage for web apps in either case.
Dead Comment
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.
Anyways, that's a great idea you have. I never knew I wanted this, but now I want it very badly.
One specifically designed for phones with a very limited feature set, though? That could be very handy.