[boost] Use of static_cast in dereferenceable

From: jsiek_at_[hidden]
Date: 2000-06-13 12:31:33

As I understand it the use of static_cast is essential. We have to
downcast the type of *this from dereferenceable<...> to const T&
so that we can get the T::operator*().

David Abrahams writes:
 > I am concerned abou the following incantation in operators.hpp:
 > 
 > template <class T, class V, class D = boost::detail::empty_base>
 > struct dereferenceable : D
 > {
 >   V* operator->() const
 >   {
 >     return &*static_cast<const T&>(*this);
 >   }
 > };
 > 
 > 
 > What is the purpose of the static_cast here? If it is useful, wouldn't it be
 > much safer to write:
 > 
 > template <class T, class V, class D = boost::detail::empty_base>
 > struct dereferenceable : D
 > {
 >   V* operator->() const
 >   { const T& x = *this; return &*x; }
 > };
 > 
 > ??
 > Thanks,
 > Dave
 > 
 > 
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