问题描述
当我尝试编译此代码时，此结构构造函数出现问题:
I have a problem with this struct contructor when I try to compile this code:
typedef struct Node
{
Node( int data ) //
{
this->data = data;
previous = NULL; // Compiler indicates here
next = NULL;
}
int data;
Node* previous;
Node* next;
} NODE;
当我来的时候出现这个错误:
when I come this error occurs:
linkedlistlinkedlist.h||In constructor `Node::Node(int)':|
linkedlistlinkedlist.h|9|error: `NULL' was not declared in this scope|
||=== Build finished: 1 errors, 0 warnings ===|
最后一个问题是结构，但它在我的 main.cpp 中工作正常，这次它在头文件中并给了我这个问题.我正在使用 Code::Blocks 来编译这段代码
Last problem was the struct, but it worked fine when it was in my main.cpp, this time it's in a header file and is giving me this problem. I am using Code::Blocks to compile this code
推荐答案
NULL 不是 C 或 C++ 语言中的内置常量.事实上，在 C++ 中它或多或少已经过时了，只需使用纯文字 0 代替，编译器会根据上下文做正确的事情.
NULL is not a built-in constant in the C or C++ languages. In fact, in C++ it's more or less obsolete, just use a plain literal 0 instead, the compiler will do the right thing depending on the context.
在较新的 C++(C++11 及更高版本)中，使用 nullptr(如评论中指出的，谢谢).
In newer C++ (C++11 and higher), use nullptr (as pointed out in a comment, thanks).
否则，添加
#include stddef.h>
获取NULL定义.
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