> 2) "#define P" is clunky for several reasons: a) why do we have to care about POD vs non-POD? Because the latter needs some equivalent to a copy constructor

> 2) "#define P" is clunky for several reasons: a) why do we have to care about POD vs non-POD? Because the latter needs some equivalent to a copy constructor and destructor. I had another reaction: there is no equivalent to a move constructor? That becomes painful when it's time to support a vector of vectors. (Don't want to do a deep copy of all elements when you resize the vector.)