C++ defines macros

C++ defines macros

• C++ macros are very useful, especially in places like logging systems.
• Macros are used during precompilation and can replace anything in the code.
• Macros are very useful, but don't overuse them, because it may make your code unreadable to others.

Here are a few examples of macro usage:

#include <iostream>

// 定义一个宏
#define WAIT std::cin.get()

int main()
{
    
    
    WAIT;
}

#include <iostream>
// 定义一个宏
#define LOG(x)  std::cout << x << std::endl

int main()
{
    
    
    LOG("Xwp is handsome");
}

This is great, you can specify some code not to participate in compilation

When I #define PR_DEBUG 1: means that LOG(x)this macro is valid, and then output information;
when I #define PR_DEBUG 0: means that LOG(x)this macro is meaningless, and no information will be output.

#define PR_DEBUG 0
#if PR_DEBUG == 1
#define LOG(x) std::cout << x << std::endl
#else
#define LOG(x)
#endif

int main()
{
    
    
    LOG("xwp is handsome");
    LOG(8);
}

In addition, the definition of the macro must be on one line. If you want to write in a new line, you need to use\

#include <iostream>

#define MAIN int main() \
{
      
      \
    std::cout << 3 << std::endl;\
}

MAIN