Genius is one of the oldest GNOME projects, it has been the original GNOME calculator before I got wild ideas about it doing absolutely everything. It is programmable has a powerful language and handles many fun features including matlab like support for matrices. It requires GNOME2 (at least glib2 if you don't want a GUI) and a recent enough gmp library. However you can still use the command line version if you prefer non-gui interface.