// should be friend of boost::exception and error_info_container_impl
template <typename E, typename B>
bool boost :: operator >> (const E & e, shared_ptr <const B> & ptr)
{
	if (exception_detail::error_info_container_impl * i = dynamic_cast <exception_detail::error_info_container_impl *> (e.data_.get()))
		for (exception_detail::error_info_container_impl::error_info_map::iterator ii = i->info_.begin(); ii != i->info_.end(); ++ii)
			if (ptr = dynamic_pointer_cast <const B> (ii->second))
				return i->info_.erase (ii), true;
	return false;
}