C++11，关于nullptr

[謠言]

很简单的一个类就能实现C++11中nullptr的全部功能，为什么新标准还要定义一个关键字呢？
标准的演进原则不是说“能用库完成的就不修改语言来实现”的吗？

struct nullptr_t
{
template<class T> operator T() const;
template<class T> operator T*() const { return 0; }
template<class T> bool equal(T) const;
template<class T> bool equal(T* p) const { return 0 == p; }
};

template<class P>inline bool operator==(nullptr_t n, P p){ return n.equal(p); }
template<class P>inline bool operator==(P p, nullptr_t n){ return n.equal(p); }
template<class P>inline bool operator!=(nullptr_t n, P p){ return !n.equal(p); }
template<class P>inline bool operator!=(P p, nullptr_t n){ return !n.equal(p); }

namespace { nullptr_t nullptr; }

[对象]

给LZ摘一段0x的文档：

Re nullptr: It must be copyable, throwable, and passable through varargs. 
• Re the type of nullptr: It should be named, and be a POD type. Named variables 
of this type are allowed. reinterpret_cast to and from this type is allowed. It is 
both a pointer type and a pointer-to-member type; i.e., it matches both a T* and a 
T::* partial specialization. If it matches two partial specializations, you have an 
ambiguity. 
• Re the name of the type of nullptr: nullptr_t is introduced as a typedef for 
decltype(nullptr). 
In addition, this paper includes proposed wording for the feature. 

原文：http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2214.pdf

[謠言]

更正nullptr_t定义：
struct nullptr_t
{
template<class T> operator T*() const { return 0; }
template<class T> bool equal(T* p) const { return 0 == p; }
};