Say I have an object a of type

  any<mpl::vector<Concept1,typeid_<>>,_self&>

and an object b of type

  any<Concept2,T>

where Concept1 is a subconcept of Concept2. Is it possible to make
a refer to b rather than the object wrapped by b? I mean:

  any_cast<void*>(&a)==&b
  typeid_of(a)==typeid(b)

A solution involving wrapping/copying b into some auxiliary entity would
be acceptable too. This questin is obviously connected to the
implementation of boost::any_collection, as Steven will undoubtedly have
guessed.

Thank you,

Joaquín M López Muñoz