This was a proposed library implementation of nullptr for c++0x from http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1601.pdf const // this is a const object... class { public: template<class T> // convertible to any type operator T*() const // of null non-member { return 0; } // pointer... template<class C, class T> // or any type of null operator T C::*() const // member pointer... { return 0; } private: void operator&() const; // whose address can't be taken } nullptr = {}; // and whose name is nullptr Very similar to your impl although I think the static_cast in yours is redundant. The standard says, 0, being an integral constant expression that evaluates to zero, is a null pointer constant which is implicitly convertible to a pointer type (4.10) Chris On 7/31/07, Michael Marcin <mike@mikemarcin.com> wrote:
Hello,
I have something like:
class A; boost::array<A*,10> the_array;
std::fill( the_array.begin(), the_array.end(), NULL );
Which wont compile (at least under Visual Studio 2005) without a cast for NULL... I've had this problem before and decided to try to find an easy cast free expressive solution for it.
After a few minutes I came up with:
namespace detail { struct null_ptr_impl { template< typename T > operator T* () const { return static_cast<T*>(0); } }; } // end namespace detail const detail::null_ptr_impl null_ptr;
std::fill( the_array.begin(), the_array.end(), null_ptr );
Does this exist somewhere already? Is it a good solution?
Thanks,
Michael Marcin
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