http://www.boost.org/libs/ptr_container/doc/reference.html I'm trying to use the boost::ptr_map class, and either I'm misunderstanding it's usage or syntax. I originally assumed that a ptr_map class is a map container of pointers and/or container of abstract objects via pointers. However, the example code in the following link, does not seem to be using pointers at all. http://www.boost.org/libs/ptr_container/doc/reference.html Moreover, if I attempt to use an abstract pointer in either the first or second type, I get compile errors. I also tried creating a ptr_map to a base class with a normal virtual function, but when I ran my test, I can see that it slices the derived class. So exactly what is the ptr_map class for, and does anyone have example code that will work with an abstract pointer? I'm trying to compare using the boost pointer containers to using a clone smart pointer. Which boost container would be able to give me functionallity like the following: map<cow_ptr<Shape>, int> mShapeToInt; map<int, cow_ptr<Shape> > mIntToShape; Where Shape is an abstract base class, and cow_ptr is the following: http://code.axter.com/cow_ptr.h