Processing variable arguments

/* 1503.c: Processing variable arguments */
#include <stdio.h>
#include <stdarg.h>

double AddDouble(int x, ...);

main ()
{
    double d1 = 1.5;
    double d2 = 2.5;
    double d3 = 3.5;
    double d4 = 4.5;

    printf("Given an argument: %2.1f\n", d1);
    printf("The result returned by AddDouble() is: %2.1f\n\n",
    AddDouble(1, d1));
    printf("Given arguments: %2.1f and %2.1f\n", d1, d2);
    printf("The result returned by AddDouble() is: %2.1f\n\n",
    AddDouble(2, d1, d2));
    printf("Given arguments: %2.1f, %2.1f and %2.1f\n", d1, d2, d3);
    printf("The result returned by AddDouble() is: %2.1f\n\n",
    AddDouble(3, d1, d2, d3));
    printf("Given arguments: %2.1f, %2.1f, %2.1f, and %2.1f\n", d1, d2, d3, d4);
    printf("The result returned by AddDouble() is: %2.1f\n",
    AddDouble(4, d1, d2, d3, d4));
    return 0;
    }
    /* definition of AddDouble() */
    double AddDouble(int x, ...)
    {
    va_list arglist;
    int i;
    double result = 0.0;

    printf("The number of arguments is: %d\n", x);
    va_start (arglist, x);
    for (i=0; i<x; i++)
    result += va_arg(arglist, double);
    va_end (arglist);
    return result;
}