AlexCalc

Try the web version here: https://alexbarry.github.io/AlexCalc/

Available on:

• Web (desktop or mobile): https://alexbarry.github.io/AlexCalc/
• Android: Google Play
• iOS: No native app yet, but for now here's how to add a home screen shortcut to the browser version on iOS.

How to use

• Complex numbers: enter rectangular form (3 + 4i) or polar (5 angle 30). The angle button replaces the i button when alt is pressed. If typing, j can be used in place of i (more info).
• Variables: store variables by typing an expression, then pressing the "store" button in the bottom left (or typing the -> operator), and then entering a variable name (e.g. 1.23e5 -> x). Then simply reference this variable name in other expressions (e.g. x^2 - 4*x -> y)
• Units: select or type a desired unit, e.g. 1 kg or 3 m s^-2. The default output is in SI units, but arbitrary unit conversion can be accomplished with the to operator (e.g. 1 kg to lb) which can be typed directly or by pressing the alt then "to units" button (which appears in place of the units button when alt is pressed). Note that the division slash (/) can not be used within units, e.g. "1 metre per second" can only be defined as 1 m s^-1, and not 1 m/s because that means "1 metre divided by variable s". This is unfortunate, but I'm not sure if there is any way to resolve the ambiguity. (Of course you are free to do 1 m / 1 s)
• Negative numbers: the "subtraction" button can also serve as a negative sign.

Discussion

Please submit comments, feedback, feature requests, or discussions to:

• Github: https://github.com/alexbarry/AlexCalc
• Reddit: reddit.com/r/AlexCalc
• Discord: discord.gg/ckNstZc2nF
• Email: alexbarry.dev2 [ at ] gmail.com
• Matrix: #alexcalc:matrix.org

How it works

• I wrote C++ to parse plaintext input (intended to be written with a keyboard or generated via button presses), like 3 + 4, sqrt(1 acre) to m or 5*cos(45) + 3i -> x into a set of nodes.
• I also wrote C++ to evaluate those nodes or convert them to plaintext LaTeX.
• I use Emscripten to compile the C++ to WebAssembly (WASM) for web, and NDK to compile to Android native code on Android.
• I use MathJax to render the LaTeX into the equation display in HTML.
• I threw together a UI in HTML and Android. There turned out to be a lot more UI specific code than I anticipated. In hindsight I should have tried to do more of it in C++.

Once the page is downloaded, there are no server side dependencies. Everything should be running locally in your browser. (However, note that if you try to save this page for offline use and then open it, it won't work. I think it's because browsers block running WASM loaded from the local filesystem, presumably for security. When I test locally I host a simple webserver, e.g. (python3 -m http.server 1234) and then navigate my browser to http://localhost:1234. If there is demand for an offline version, or something I can do to help browsers save the page for offline use, please let me know!)

Feedback, alternatives?

Please let me know if this is valuable to you (and what features are useful, and what are not useful or are buggy), or if a better alternative exists. This is something that I wanted for myself many years ago when I was in school, specifically to input polar complex numbers with degrees, either on my phone or PC.

The best I had at the time was an annoyingly expensive graphing calculator that I'd often forget to bring with me to class, or a PC running some programming language. Both of these had variables, neither had unit support. I remember it being particularly painful to enter polar complex numbers with the angle specified in degrees, I vaguely remember doing something like e^(angle_in_degrees/1 radian).

The equation display also seems like a nice feature, since I'd often end up having to count seemingly endless brackets when entering even relatively simple formulas.

The units I threw in because it seemed like it should be easy, only to constantly get frustrated when dealing with things like degrees/radians and frequency in Hertz or radians/seconds, or wondering if multiplying by 1 degree Celsius should be the same as multiplying by 1 Kelvin (interpreting it as a change in temperature), or by 274 Kelvin (interpreting it as an absolute temperature).