Re: [Boost-users] polymorphic_downcast and references

From: Michael Marcin (mike_at_[hidden])
Date: 2007-03-21 04:43:31

Gennadiy Rozental wrote:
> "Michael Marcin" <mike_at_[hidden]> wrote in message 
> news:etqf0t$6ea$1_at_sea.gmane.org...
>> Unless I'm missing something it looks like polymorphic_downcast doesn't
>> provide an overload for reference types... is there a reason?  This
>> makes it a little inconvenient for use.
> 
> I brought this up some time ago. No one seemed to care enough to work on 
> docs update. As usual in many volunteering based projects ;)
> 
> R u up to it?
> 

Is the problem the docs or the lack of an overload supporting 
references?  Shouldn't something like this work?

#include <boost/type_traits/remove_reference.hpp>
#include <boost/type_traits/add_pointer.hpp>
#include <boost/utility/addressof.hpp>

namespace boost
{
template <class Target, class Source>
inline Target polymorphic_downcast( Source& x )
{
        BOOST_ASSERT( dynamic_cast< typename add_pointer< typename 
remove_reference<Target>::type >::type >( addressof(x) ) == addressof(x) 
);  // detect logic error
        return static_cast<Target>(x);
}
} //end namespace boost

Thanks,

Michael Marcin