I would like to create a portable library for iPhone, that also could be used for other platforms.
My question is the fallowing:
Does anyone knows what is the be
Go for C or C++ - I do not see any reason for recommending one over the other without knowing more about your goals.
In terms of memory usage, C++ and C do demand more disciplined coding. In terms of speed, C and C++ will in virtually any case be faster than any ObjC/ObjC++ solution. I do frequently mix my Objective C applications with C and C++ code and was always pleased with the results. As Jonathan correctly stated, ObjectiveC++ is mostly a bridge for using C++ code/libraries within your Objective C application/s.
You can freely use C++ objects from within Objective C++. You can however NOT use Objective C/C++ objects within C++. So its a one-way-road. To overcome any limitations imposed by this restriction, simply wrap your C++ objects with Objective C++ classes where needed.