What is the best open-source equivalent for Mathematica? My requirements are:
- (most important) Must be a real computer algebra system (CAS). Notably, I don't want Matlab clones -- I want something that can, at least, symbolically differentiate and integrate.
- Must be programmable. A functional-programming view of the world, like Mathematica's, would be awesome. The basic datatype of M'ica is the list, which is very convenient!
- (least important) Similar syntax would be nice.
The ability to deal with objects such as groups or graphs would be a great bonus, but my primary emphasis is on the main things Mathematica and Maple do: algebra and calculus, both symbolic and numeric. Also, plotting is not high on my list of requirements, as I'm mostly a terminal and not GUI user.