有如下C++代码：
#include <iostream>
using namespace std;
#define A(exp) cout << "I am "#exp << endl;
#define B(exp) cout << sz##exp << endl;
#define C(exp) cout << #@exp << endl;
int main()
{
char *szStr = "test";
A(Chinese); // cout << "I am ""Chinese" << endl;
B(Str); // cout << szStr << endl;
C(a); // cout << 'a' << endl;
C(ab); // cout << 'ab' << endl;
return 0;
}运行结果如下：
展开的时候，#exp被扩展成
字符串
，##exp被扩展成
子串
，#@exp被扩展成
字符
。
注意：
#@只实用于windows系统
，MSDN如下说明
|
Operator |
Action |
|---|---|
|
Stringizing operator (#) |
Causes the corresponding actual argument to be enclosed in double quotation marks |
|
Charizing operator (#@) |
Causes the corresponding argument to be enclosed in single quotation marks and to be treated as a character (Microsoft Specific) |
|
Token-pasting operator (##) |
Allows tokens used as actual arguments to be concatenated to form other tokens |
可用作自定义ASSERT：
#include <iostream>
using namespace std;
#ifdef ASSERT
#undef ASSERT
#endif
#define ASSERT(exp)\
if (!(##exp))\
{\
cout << "an error occured while execute \""#exp"\" at "\
<< __FILE__ << "(" << __LINE__ << ")" << endl;\
exit(-1);\
}
int main()
{
int a = 0;
int b = 1;
ASSERT(a == b);
cout << "test" << endl;
return 0;
}结果如下：
