Dynamic polymorphism in C++ requires that objects (such as instances
of classes derived from an abstract base) be accessed through an
indirection pointer because their actual type and size are not known
at the point of usage. As a consequence, regular containers cannot
store polymorphic objects directly: the usual workaround is to have
containers of pointers to heap-allocated elements.

When the particular traversal order is not relevant to the user
application, Boost.PolyCollection proposes an alternative data
structure that restores memory contiguity and packs elements according
to their concrete type. Three container class templates are provided:

- boost::base_collection
- boost::function_collection
- boost::any_collection

respectively dealing with three different types of dynamic polymorphism available in C++:

- Classic base/derived or OOP polymorphism.
- Function wrapping in the spirit of std::function.
- So-called duck typing as implemented by Boost.TypeErasure.

The interface of these containers closely follows that of standard
containers.