I used the CE C toolchain developed by members of the community (https://github.com/CE-Programming/toolchain). This allowed me to program in C and not worry about any hooks. The toolchain compiles the code and cleverly compresses and decompresses it so that it can execute on the calculator despite the fact that the decompressed binary is 117721 bytes! Much larger than the usual ~64kb limit. It executes as a program, not an app, and I haven't had any problems with that yet thanks to the great work by the toolchain programmers

PineappleCAS v1.0 is released! You can download it here: https://github.com/nathanfarlow/PineappleCAS/releases   

Hello!

You might know me from the Symbolic Derivative Project. I thought I could do better so I am working on a CAS (computer algebra system) for the TI 84+ CE. It is nearly done and I want to tease a little bit about the progress and work I still have to do before it is released. It is called PineappleCAS and you can check it out here: https://github.com/nathanfarlow/PineappleCAS

It can already simplify algebra identities and like terms, manipulate complex numbers, expand things (A+B)(B+C) or (A+B)^8, evaluate large constants like 2 * 3 ^ 1001 or 100! that the calculator cannot do normally, and can take derivatives that are completely simplified and beautifully exported to avoid necessary multiplication signs or parentheses and look way better than the result of the previous project.

You will be able to pass arguments to PineappleCAS from a TI BASIC program to operate on algebra from within a TI BASIC program.

The only things that I need to finish is the TI-BASIC interface.

Here are some screenshots: