问题描述
实际上，我正在编写所有库类的自己的版本，并且我不想将STL文件包括在类文件中.因此，例如，我想检查节点是否等于null.如果我写类似
Actually I am writing my own version of all library classes, and I don't want to include the STL files into my class file.So, for example, I want to check whether the node is equal to null.If I write something like
#define nullptr 0
然后它无法与其他节点指针(即Node *root = nullptr)一起使用
Then it is not working with some other node pointer (i.e. Node *root = nullptr)
推荐答案
书中提到的操作方法:项目25:避免在指针和数字类型上重载" ".
How to do that is mentioned in the book: Effective C++, 2nd edition by Scott Meyers (newer edition is available) in chapter: "Item 25: Avoid overloading on a pointer and a numerical type.".
如果您的编译器不知道 nullptr 由C ++ 11引入的关键字.
It is needed if your compiler doesn't know the nullptr keyword introduced by C++11.
const /* this is a const object... */
class nullptr_t
{
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; /* Can't take address of nullptr */
} nullptr = {}; /* and whose name is nullptr */
那本书绝对值得一读.
与 nullptr 的优势://en.cppreference.com/w/cpp/types/NULL"rel =" nofollow noreferrer> NULL 是，nullptr的作用类似于真实的指针类型，因此它增加了类型安全性，而NULL就像一个整数，在C ++ 11之前的版本中设置为0.
The advantage of nullptr over NULL is, that nullptr acts like a real pointer type thus it adds type safety whereas NULL acts like an integer just set to 0 in pre C++11.
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