Macros.md

Macros in C++

In the Preprocessor pass, the compiler basic make a 'text-edit' stage, in which we control what code is fed to the next compile stage. It basic is a find and replace but with a little more control.

Templates are evaluated later than Macros.

Macros, being such a broad an open subject, it can be used in different levels of complexity (like Templates), and as such, can decrease our code readability, specially for people that aren't used to it.

We can give values for our Preprocessor macros

#define PR_DEBUG 0

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

int main()
{
    LOG("Hello");
    std::cin.get();
}

Or we can define our Preprocessor values

#define PR_DEBUG

#ifdef PR_DEBUG
#define LOG(x) std::cout << x << std::endl;
#else
#define LOG(x)
#endif

int main()
{
    LOG("Hello");
    std::cin.get();
}

We can use multiline macros, just by inserting a \ to escape the \n (also, don't leave any trailing spaces after the backslash, otherwise we will escape that space)

#define MAIN int main() \
{\
    std::cin.get();\
}

MAIN