how to handle variable length argument in c 2b 2b

1#include <cstdarg>
2#include <iostream>
3 
4using namespace std;
5 
6// this function will take the number of values to average
7// followed by all of the numbers to average
8double average ( int num, ... )
9{
10  va_list arguments;                     // A place to store the list of arguments
11  double sum = 0;
12 
13  va_start ( arguments, num );           // Initializing arguments to store all values after num
14  for ( int x = 0; x < num; x++ )        // Loop until all numbers are added
15    sum += va_arg ( arguments, double ); // Adds the next value in argument list to sum.
16  va_end ( arguments );                  // Cleans up the list
17 
18  return sum / num;                      // Returns the average
19}
20int main()
21{
22    // this computes the average of 13.2, 22.3 and 4.5 (3 indicates the number of values to average)
23  cout<< average ( 3, 12.2, 22.3, 4.5 ) <<endl;
24    // here it computes the average of the 5 values 3.3, 2.2, 1.1, 5.5 and 3.3
25  cout<< average ( 5, 3.3, 2.2, 1.1, 5.5, 3.3 ) <<endl;
26}
27