Pi Cubed 1.1 now on the App Store

Pi Cubed icon

Pi Cubed version 1.1 made it on the App Store today. This is a significant update, adding one of the major features that I had planned for the application: the ability to create your own custom equations and save those equations within your own equation library. It also adds support for plotting equations by handing them off to Grafly, if you have that application installed on your device.

Custom equations and categories

I had planned to include support for user-defined equations and categories from the beginning, but this support required some significant user interface additions. My initial focus with Pi Cubed was on its numerical calculation capabilities, with the equation abilities second to those. After launch, many people wrote or posted in the forums requesting this capability, though, so I made it my priority.

Within equations, you can now insert variables by clicking on the 'x' menu item. Variables can be edited by tapping on the edit button within the variable description, including specifying subscripts and the variable description. Greek letters are automatically parsed from their English description into the proper characters.


These custom equations can be stored in the list of recent calculations or within the new custom equation library. The interface of the entire equation library has been overhauled to support the addition of this new section. It now uses a tab-based system to let you quickly switch between the recent calculations, the built-in equation library, and the custom library.

Within the custom library, you can create, rename, and delete categories of equations. Equations can be stored to these categories and moved between them. This should be ideal for students wanting to create an easy reference for upcoming tests, or scientists who want to store and organize commonly used equations.

Grafly plotting


By working with the friendly developers at Em Software, Pi Cubed is now able to export equations to Grafly for plotting. If you have Grafly installed on your iPhone / iPod touch, you can now send custom equations directly to Grafly for 2-D or 3-D plotting.

The only restriction on the equations is that they must be specified in terms of x, y, and z. Aside from that, Grafly has an extremely powerful equation parsing and plotting engine that should be able to handle most of the equations you throw at it.

Angle units


Also by popular request, I've added the ability to specify the default unit for angle calculations. This is found within the Settings application, under the Pi Cubed grouping.

Other improvements

The overall animations for equation and number entry have been cleaned up. Additionally, the equations are laid out in a cleaner manner within the library categories. Finally, the memory usage of the application has been reduced and the overall application has been tweaked to function well on the upcoming iPhone OS 3.0.

More information

The manual within the application and on this site have been updated, if you wish to read more about the new capabilities of Pi Cubed.

Two of the nice icons you see on the equation library tab bar come from the set published by Glyphish. I recommend checking them out if you need icons like this in your application, especially when the author releases the vector graphics files for them. If you find them useful, as I did, please donate a little to reward the designer for his work.


This app is now in the 'buy' column for me. I was holding off until custom equations were supported - now I no longer have an excuse! Please keep up the good work and I'll actively promote this app with my colleagues.

Same here, been using illegal version of the app till now.
I have just purchased a legal copy of Pi cubed app, and I can say with 100% certainty that it is my favorite app now.
Hope to see more new improovements soon.

Thanks, guys. Yes, I do have quite a bit more planned for the future versions of the application, including unit support for numbers and a whole mess of features enabled by iPhone OS 3.0.

Downloads from Appulous and the torrents actually don't bother me that much. I know that there are many students out there who would never pay for the application in the first place, but by downloading and using the application I hope that they'll show it off to people who will. I'm somewhat proud of the fact that Pi Cubed has been downloaded so many times through those channels, which at least shows that people are interested in it. As you state, for some of those folks it eventually becomes a worthwhile purchase.

Yeah! It's truly amazing. But Mathematica is far more powerful.

Are you planning to include integration, differentiation, normalising vectors etc? If not, I've got some programming to do.

True symbolic math is something I plan to get to in version 2.0, but that's a long ways off. Vector math may come in at around the time I get matrix math supported, which won't be quite as long.

When you start talking symbolic math, unless you're leveraging an existing computer algebra system like Mathomatic or Maxima, you've got a lot of programming to do. There's a reason why applications like Mathematica and Maple cost what they do. I wrote my own math engine for this application, and even with it only focused on numerical calculations it took months to assemble.

Since the time I wrote that comment, I've installed the iPhone SDK, compiled GMP, CLN and GiNaC from source and got the GiNaC CAS working on the iPhone.

Just differentiated (Sinh(x^x^x))^3 with it on the simulator and it seems to work fine.

GiNaC is released under the GPL, but the GPL states that software can be charged for, so long as the source code is also available for no cost, and that the users are then free to redistribute the source code, whether they charge for it or not is up to them.

The way I see this working with the app store is to display a message or link to a website with the source code for the application in the application itself.

The users will be able to see and effectively compile the code for themselves if they wish, and even put it back up on the appstore for free if they wanted to. The main reasons I can see this not happening is that

a) it's the iPhone. Recompiling someone else's source code and redistributing it for free is troublesome to say the least.

b) ALL the libraries I used I had to compile from source, and put it this way; there was MINIMAL support. GMP has hundreds of problems with compilation, CLN and GiNaC are little better.

c) Redistributing my program for free wouldn't be that annoying, really. I would consider the price more like a donation for my work on making it.

Not to mention the fact I will tell the GiNaC community of my plight, finally managing to get all the prerequisites of GiNaC and GiNaC itself to compile from source on Leopard, and how I wish to make something for the iPhone, and if the app store turns out to be totally incompatible with the GPL, hopefully we can come to some sort of dual-license agreement.

Have you tried this on an actual iPhone or iPod touch? Beware that you may run into incompatibilities when you actually install this on an iPhone, whether from Intel-specific assumptions in their code, or from libraries that aren't present on the device. The Simulator uses the full capabilities of the Mac, including elements that may not be there on the iPhone itself.

Performance is a second concern. Generally, low-level C libraries perform well, but for the more complex operations you're describing, you may run into some issues with hardware limitations in memory or CPU speed.

Finally, there is the user interface. This was the most important component to me, as I had tried products like Mathomatic (which leverages an existing CAS library) and found them difficult to use in the kind of situations I use my device. That's why I came up with my own custom interface and layout engine, because I wanted to have something more than a plain text field for input and evaluation of these calculations. More than half of the time spent on this application was in the crafting of the user interface. Even with a solid math parsing library, you'll need to make it accessible to a touch interface somehow.

The only libraries GiNaC use are CLN, GMP, and the standard library. All these are C++ libraries. I deliberately compiled all these from source as if I was not using an intel machine.

Hopefully performance won't be an issue, but I'll need to sign up as a developer to check, I guess!

And yes, the user interface will most likely be the vast majority of the programming that I do. After watching the video for Pi Cubed, I was kind of inspired to write something like it myself, whether it works on an actual iPhone or not to me isn't as important as writing the program itself.

It'll be the first thing I've ever written for the iPhone, so I'm treating it more as a learning exercise than a lucrative business venture.

Thanks for your replies by the way!

I usually don't pay for applications but I bought pi cubed after looking at reviews and I have no regrets. Great application.

But sometimes I wish there was an "undo" button somewhere. When I tap a function I didn't mean to and want to go back a step, life gets a little hard. Do you plan on adding anything like that by any chance?

In fact, that's the very next thing I'm working on. I will be reworking the underlying data model to support undo, which should also significantly reduce the startup time for the application.

My current plan is to use the iPhone 3.0 "shake-to-undo" interaction method to trigger the undo / redo actions.

very interesting - looks like a great aplication.

Great application in deed. I too generally don't purchase applications. But this was certainly worth the money. Thanks for it.

Thanks a lot for this useful post, the info is pretty good and this applications seems great i will recommend it to my nephew, he was looking for an app like this.

Looks pretty amazing. The amount of apps on the iphone is absolutely staggering. Things like this are just so helpful. Thanks

I cannot find Grafly

Has it been taken off the App Store?

If so what can I use in place of it.

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