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Simple program to illustrate variadic macros In C

/*
 * C99 has  support of variable arguments in macros statement
 * (called variadic macro) just like variable argument function, Macros also 
 * can be of variable number of augments
 * This program illustrate variadic macros
 */

#include <stdio.h>
  /*
  * Simple Macro definition
  * which allows to print whatever the way you want
  *  in Macro definition "..." indicates variadic macro, OP() definition is 
  * mixture of named args and variable number of aguments, it is possible
  * to have macro of complete variable number of args
  * like DISPLAY in below example
  */

#define OP(format, exp, ...)  printf(format, exp, ##__VA_ARGS__)
#define DISPLAY(...)    printf(__VA_ARGS__)
int main()
{
 int a=3, b=4, c=5;

 OP("%s %d\n", "Result after add", a+b);
 OP("%s %d %s %d\n", "Result after add", a+b+c, "Result after sub", a-b);
 OP("%s\n", "This is test program");
 OP("%s %f\n", "Division of a/b", a/(double)b);
 OP("%s %s %s %s\n", "This", "is", "Variadic", "Macro");

 /* This show why we used ## token paste operator at macro definition, 
  * our definition indicates  2 mandatory args and variable number of args, 
  * if we left out variable argument in macro statement(in case if we have only
  * mandatory args) program will not compile, as in below statement, such  
  * cases ## will come to resuce, ## operator has a special meaning
  * when placed  between a comma and a variable argument, in case if we
  * don't have variable argument, ## will delete the comma (,) between
  * last mandatory argument and __VA_ARGS__
  */
 OP("%s\n", "Only two args"); 

 DISPLAY("%s %s\n", "Variadic", "Macro only");

 return 0;
}



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