C++: converting a container to a container of different yet compatible type

Question

It often happens to me to have a a container C (or whatever kind of wrapper class, even smart pointers) for a type T1, and want to convert such

Answer 1

This is indeed difficult for containers. Type compatibility is not enough, types actually need to be identical in memory to prevent slicing when assigning. It might be possible to implement a ptr_container that exposes pointers of a compatible type. For example, boost's ptr_containers keep void*s internally anyways, so casting them to compatible pointers should work.

That said, this is definitely possible with smart pointers. For example, boost::shared_ptr implements static_pointer_cast and dynamic_pointer_cast.