I mention in the sticky here that the underlying language is C++. I think it's an important point to make (which is why it is point #1).
With the exception of exceptions (lol) most other things can be done, and done easily. For example, you can use the STL if you download Andy Brown's port of it (The Standard Template Library (STL) for AVR with C++ streams ).
If you can use that (which relies heavily on templates) you can do pretty-much anything.