Variadic Function

In C, as in other programming languages, there is a concept called a variadic function, which is a function that accepts an unlimited number of parameters.

To use a variadic function, we first need to include the <stdarg.h> header file.

Let's look at an example to see how this works:

#include <stdio.h>
#include <stdarg.h>
int sum(int num, ...) {
   va_list list;        
   va_start(list, num);
   int sum = 0;
   for (int i = 0; i < num; i++) {
       sum += va_arg(list, int); 
   }
   va_end(list); 
   printf("%d", sum);
}
int main() {
    sum(2, 20, 30);          
   return 0;
}

In this example, the sum function calculates the sum of a variable number of integer values.

1. Declare a variable to hold the argument list using the <strong>va_list</strong> macro:

   va_list list;

2. Initialize the argument list:

   va_start(list, num);

3. Declare a variable to hold the sum:

   int sum = 0;

4. Loop through all the elements, retrieve each argument, and add it to the sum:

   for (int i = 0; i < num; i++) {
          sum += va_arg(list, int); 
      }

5. Clean up the argument list after the calculations are done:

    va_end(list); 

6. In the <strong>main</strong> function, call the <strong>sum</strong> function like this:

     sum(2, 20, 30);