Michael Marcin wrote:
Chris Fairles wrote:
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)
Cute. It might be nice to have this as a Boost utility library.
Interestingly that implementation fails for my test case because: [temp.arg.type] 14.3.1 Template type arguments 2 A local type, a type with no linkage, an unnamed type or a type compounded from any of these types shall not be used as a template-argument for a template type-parameter. So it must be named to be useful as an argument to say std::fill. - Michael Marcin