Looking at a class like Region (Region.cpp) there are calls to get the parent region and sub regions, there are instances where a Region will not have a parent or subs. The current API returns shared_ptr that may be nullptr or a Region.
Since we are trying to make an effort towards values over pointers should be considered some changes here? Obviously a reference is out of the question because it can't be null. A value is really out of the question too since it can't be null and making a sentinel value is not a great solution. Raw pointers are fine since they can be nullptr but make ownership ambiguous. Using shared_ptr is good since it can be nullptr and solves the ownership problem. Another option is to embrace the forthcoming std::optional available as boost::optional in C++11. I am leaning towards keeping it shared_ptr since using boost::optional would require users compile with boost. I don't think we should have anything on our API that is not ours of C++11. Requiring third party libraries to compile against our API doesn't fly right by me. Thoughts?
