Preprocessor Macros

Preprocessor Macros

//http://www.tutorialspoint.com/cprogramming/c_preprocessors.htm

#define	  Substitutes a preprocessor macro
#include	Inserts a particular header from another file
#undef	  Undefines a preprocessor macro
#ifdef	  Returns true if this macro is defined
#ifndef	  Returns true if this macro is not defined
#if	      Tests if a compile time condition is true
#else	    The alternative for #if
#elif	    #else an #if in one statement
#endif	  Ends preprocessor conditional
#error	  Prints error message on stderr
#pragma	  Issues special commands to the compiler, using a standardized method

---

#define MAX_ARRAY_LENGTH 20

#undef  FILE_SIZE
#define FILE_SIZE 42

#ifndef MESSAGE
   #define MESSAGE "You wish!"
#endif

#ifdef DEBUG
   /* Your debugging statements here */
#endif

//Continuation (multiple lines)

#define  message_for(a, b)  \
    printf(#a " and " #b ": We love you!\n")

//Parametrized Macros

#define square(x) ((x) * (x))

#define MAX(x,y) ((x) > (y) ? (x) : (y))