Re: nullptr placeholder without #define
On 6 Mar, 09:22, "marcin.sfi...@gmail.com" <marcin.sfi...@gmail.com>
wrote:
I realy did not intend to simulate nullptr in such detail but it won't
hurt I suppose.
Current version looks like this:
const class nullptr_t {
public:
template<class T>
operator T*() const { return 0; }
template<class T, class U>
operator T U::*() const { return 0; }
private:
void* p;
void operator&() {}
} nullptr = nullptr_t();
nullptr should be constant (or more specifically it should be a literal)
and obtaining its address shouldn't be possible. I've also overloaded
operator!= ;).
Your nullptr still has a few semantical differences from the C++0x
equivalent per the latest draft:
if(nullptr); // implicit conversion to bool
Solution: operator bool() const { return false; }
nullptr_t(0); // conversion from integral null pointer
// constant to nullptr_t
Solution: declare a private nested (incomplete) type Z, and a ctor
accepting a pointer to Z. Unfortunately, the class will no longer
support an initializer with braces, which nullptr_t does.
reinterpret_cast<int>(nullptr); // nullptr_t can be explicitly
// converted to integral types
Solution: Seemingly impossible.
I think that's almost as close as you can get :)
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