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 thing that I need to finish is the TI-BASIC interface.
Here are some screenshots:
