Almost no one has done that calculator app, properly. When I mean properly, I mean a complete calculator, like the TI-89.
I am using, in Android, and emulator for the TI-89 calculator.
Because no Android app has half the features, and works as well.
I am using, in Android, and emulator for the TI-89 calculator.
Because no Android app has half the features, and works as well.
But for some reason the authors of calculator apps never optimize them for the number of keypresses, unlike Casio/TI/HP. It's a lost art. Even a simple operator repetition is a completely alien concept for new apps. Even the devs of the apps that are supposed to be snappy, like speedcrunch, seem to completely misunderstand the niche of a calculator, are they not using it themselves? Calculator is neither a CAS nor a REPL.
For Android in particular, I've only found two non-emulated calculators worth using for that, HiPER Calc and 10BA by Segitiga.Pro. And I'm not sure I can trust the correctness.
Plus of course not having to do even more arithmetic when one site gives me kilograms and another gives me ounces.
Random example off the top of my head to show off some features: say it takes 5 minutes to get to space, and I heard you come around every 90 minutes, but there's differing definitions on whether space is 80 or 100 km above the surface, then if you're curious about the G forces during launch:
(2*pi*(6350+ 90±10)km / 90 minutes) / 5 minutes to gees
((2 × pi × ((6350 + 90±10) kilometers)) / (90 minutes)) / (5 minutes) ≈
2.5470±0.0040 gees
It understands unicode plusminus for uncertainty tracking, units, function calls like log(n,base), find factors, it will do currencies too if you let it download a table from the internet... I love this software package. (No affiliation, just a happy user who discovered this way too late in life)
It's not as clever as WolframAlpha, no natural language parsing or Pokédex functions (sometimes I do wish that it knew things like Earth radii), but it also runs anywhere and never tells you the computation took too long and so was cancelled
Edit: I just learned there's now also an Android app! https://github.com/jherkenhoff/qalculate-android | https://f-droid.org/packages/com.jherkenhoff.qalculate/ I've checked before and there wasn't back then, so this is cool. This version says it supports graph plotting which the command-line version doesn't do
My only gripe with it is that it doesn't solve compounding return equations, but for that one can use an emulated HP-12c.
I still have my actual HP, but it seems to chew batteries now.
[1] - https://play.google.com/store/apps/details?id=com.algeo.alge...
Classic algebraic calculators are able to to things like:
57 x = (displays the result of 57x57)
3 = (repeats the multiplication and displays 57x3)
[+/-] MS (inverts the result and stores it in the memory without resetting the previous operation)
7 = (repeats the multiplication for 7 and displays 57x7)
7 [1/x] = (repeats the multiplication for 1/7, displays 57/7)
That's what you do with the classic calculators. Often, you are not even directly calculating things, you're augmenting your intuition and offloading a part of the problem to quickly explore its space in a few keypresses (what if?..), give a guesstimate, and do some sanity checks on whether you're in the right ballpark, all at the same time. Graphing, dimensional analysis in physics, error propagation help a lot in detecting bullshit in your estimates as quickly as possible. If you're also familiar with numerical methods, you can do miracles at the speed of thought. Slide rules were a lot like that as well.
People who do this might not be your target audience, though.
Performing arithmetic on arbitrarily complex mathematical functions is an interesting area of research but not useful to 99% of calculator users. People who want that functionality with use Wolfram Alpha/Mathematica, Matlab, some software library, or similar.
Most people using calculators are probably using them for budgeting, tax returns, DIY projects ("how much paint do I need?", etc), homework, calorie tracking, etc.
If I was building a calculator app -- especially if I had the resources of Google -- I would start with trying to get inside the mind of the average calculator user and figuring out their actual problems. E.g., perhaps most people just use standard 'napkin math', but struggle a bit with multi-step calculations.
> But for some reason the authors of calculator apps never optimize them for the number of keypresses, unlike Casio/TI/HP. It's a lost art. Even a simple operator repetition is a completely alien concept for new apps.
Yes, there's probably a lot of low-hanging fruit here.
The Android calculator story sounded like many products that came out of Google -- brilliant technical work, but some sort of weird disconnect with the needs of actual users.
(It's not like the researchers ignored users -- they did discuss UI needs in the paper. But everything was distant and theoretical -- at no point did I see any mention of the actual workflow of calculator users, the problems they solve, or the particular UI snags they struggle with.)
Marvis on iOS is pretty good at this. I use it to shuffle music with some rules ("low skip %, not added recently, not listened to recently")[0] and it always does a good job.
[0] Because "create playlist" is still broken in iOS Shortcuts, incredibly.
I tried to make a joystick controller for a particular use case on one platform (Linux) and I gave up.
VLC solves a hard problem. Supporting lots of different libs, versions, platforms, hardware and on top of that licensing issues.
https://github.com/vanilla-music/vanilla >Note: As of 23. Jun 2024, Vanilla Music is no longer available in the Google Play store: I simply don't have time to comply with random policy changes and verification requests. Any release you see there is probably an ad-infested fork uploaded by someone else.
To create and add to one: long-press on a file/folder/track/album for the context menu or use the ... menu while in the now playing screen.
I’m with you in that I think shuffle should be a single list of all songs, played in a random order. But that requires maintaining state, detecting additions and updating the list, etc.
Years ago, a friend was adamant that shuffle should mean picking a random song from the list each time, without state, and if that means the same song plays five times in a row, well, that’s what random means.
To me “shuffle” is a good metaphor because a shuffled deck of cards works a specific way (you’d be very surprised to draw the same card twice in a row!)
But these things are implemented by programmers who sometimes start with implementation (“random”) and work back to user experience. And, for a specific type of technical person, “with replacement” is exactly what they’d expect.
On the whole programmers given a source of random bytes and told to pick any of 227 songs at random using this data will take one byte, compute byte % 227 and then be astonished that now 29 of the songs are twice as likely as the others to be chosen†.
In a class of fifty my guess is you're lucky if one person asks whether the random bytes are cheap (and so they should just throw away any that aren't < 227) showing they know what "random" means and all the rest will at least attempt that naive solution even if some of them try it out and realise it's not good enough.
† As a bonus in some languages expect some solutions to never pick the first song, or never pick the last song.
> you're lucky if one person asks whether the random bytes are cheap (and so they should just throw away any that aren't < 227)
If you can't deal with the 10% overhead from rejection sampling (assuming your random bytes are uniform), I guess you could try mushing that entropy back into the rest of your bytestream, but yuck.
In Rust this abuse would either "work" or panic telling you that er, that's not a coherent ordering so you need to stop doing that. Not certain whether the panic can only arise in debug builds (or whether it would detect this particular abuse, it's not specified whether you will panic only that you might if you don't provide a coherent ordering).
In C++ this is Undefined Behaviour and there's a fair chance you just introduced an RCE vulnerability into your codebase.
https://stackoverflow.com/questions/962802/is-it-correct-to-...
An example of this out in the wild: https://www.robweir.com/blog/2010/02/microsoft-random-browse...
Any info on how can I achieve this
E.g. you have 4 items. You shuffle them to get a random permutation:
4 2 1 3
Note: these are not indices, but identifiers. Let's say you go through the first two items:
4 2 <you're here> 1 3
And two new items arrive. You insert each item into a random position among the remaining items. E.g:
4 2 <you're here> 5 1 6 3
If items are to be deleted, there are two cases: either they have already been visited, in which case there's nothing to do, or they're in the remaining list, in which case you have to delete them from there.
> You insert each item into a random position among the remaining items
Thinking about shuffle + adding, I would have thought "even if it's added to a past position", e.g.
`5 4 6 21 3` as valid.
What do folks expect out of shuffle when it reaches the end? A new shuffle, or repeat with the same permutation?
I don’t think that provides a totally clear answer to “what happens at the end”, but for me it’d lean me towards “a new shuffle”, because for me most of the time a shuffled deck of cards draws its last card, the deck will be shuffled again before drawing new cards.
You should be able to accomplish this with trivial amounts of state (as in, somewhere around 4 ints).
As an example, I'm envisioning something based on Fermat's little theorem -- determine some prime `p` at least as big as the number of songs you have (N), then to determine the next song, use n := a*n mod p for fixed choice of 1 < a < p, repeating as necessary as long as n > N. This should give you a deterministic permutation of the songs. When you get back to the first song you've played, you can choose to pick a new `a` for a new shuffle, or you can just keep that permutation.
If the list of songs changes, pick new a, p, and update n to be the new position of your current song (and update your notion of "first song of this permutation").
(Regarding why this works: you want {a} to be a generator for the multiplicative group formed by Z/pZ.)
Linear congruential generators have terrible properties if you care about the quality of your randomness, but if all you're doing is shuffling what order your songs play in, they're fine.
Say I have a 20 song list, and after listening to 15 I add five more. How does this approach only play the remaining 10 songs (5 that were remaining plus 5 new)?
It doesn't. If you add 5 more songs, then the algorithm as presented will just treat it as if you're starting a new shuffle.
If you genuinely need to keep track of all the songs you've already played and/or the songs that you have yet to play, then I'm not sure you can do much better than keeping a list of the desired play order, randomized via Fisher-Yates shuffle each time you want a new shuffled ordering -- new songs can be appended to said list and shuffled in with the as-yet-unplayed songs.
You probably shouldn't have quoted "detecting additions and updating the list, etc." then.
This has some obvious downsides (e.g. an empty slot that was skipped when played and filled by a later insert won't be played), but it handles both insertion and deletions without replaying songs and you only need to store a single integer.
Many approaches that guarantee that property have pathological behavior if, say, you add a new song to your library after each song that you've played.
Edit: I checked I can also shuffle a folder without adding it to the library.
pkg install mplayer
cd /sdcard/Music
find -type f | shuf | head -1 | xargs mplayer
- It generates a list of all files in the current directory, one per line
- Shuffles the list
- Takes the top entry
- Gives it to mplayer as an argument/parameter
Repeat the last command to play another random song. For infinite play:
while true; do !!; done
You can also stick these lines in a shell script, and I seem to remember you can have scripts as icons on your homescreen but I'm not super deep into Termux; it just seemed like a trivial problem to me, as in, small enough that piping like 3 commands does what you want for any size library with no specialised software needed
I have many thousands of mp3s on my phone in nested folders. PowerAmp has a "shuffle all" mode that handles them just fine, as well as other shuffle modes. I've never noticed it repeating a track before I do something to interrupt the shuffle.
Earlier versions (>~ 5 years ago) seemed to have trouble indexing over a few thousand tracks across the phone as a whole, but AFAIK that's been fixed for awhile now.
My personal favorite feature that I got addicted to back when I was using Amarok in KDE 3 was the ability to have a playlist and a queue that resumes to the playlist when exhausted. Then I can listen to an album in order, and then go back to shuffling my driving music playlist when that's done.
I've been working on it for what will be a decade later this year. It tries to take all the features you had on these physical calculators, but present them in a modern way. It works on macOS, iOS, and iPad OS
With regards to the article, I wasn't quite as sophisticated as that. I do track rationals, exponents, square roots, and multiples of pi; then fall back to decimal when needed. This part is open source, though!
Marketing page - https://jacobdoescode.com/technicalc
AppStore Link - https://apps.apple.com/gb/app/technicalc-calculator/id150496...
Open source components - https://github.com/jacobp100/technicalc-core
Where I am standing, that never happened, but that would require that a simply staggering number of people be classified as unreasonable.
https://play.google.com/store/apps/details?id=uk.co.nickfine...
e^100 + 1 - e^100Built-in Android calculator does.
They are incomparable. TI-89 has tons of features, but can't take a square foot to high accuracy.
But, I agree I almost never want the full power of Mathematica/sage initially but quickly become annoyed with calc apps. The 89 and hp prime//50 have just enough to solve anything where I wouldn’t rather just use a full programming language.
Thanks for the heads up, I will be testing it for a few months, to see if it can replace the TI-89 emulator as my main calculator.
Edit: that calculator gives a result of 0 on this test
https://en.wikipedia.org/wiki/Derive_(computer_algebra_syste...
Edit: and Maxima as well on the mac (to back up another user's comment)