/* Fig. 14.2: fig14_02.c
   Using variable-length argument lists */
#include <stdio.h>
#include <stdarg.h>

double average( int i, ... ); /* prototype */

int main()
{ 
   double w = 37.5; 
   double x = 22.5; 
   double y = 1.7;  
   double z = 10.2; 

   printf( "%s%.1f\n%s%.1f\n%s%.1f\n%s%.1f\n\n",
      "w = ", w, "x = ", x, "y = ", y, "z = ", z );
   printf( "%s%.3f\n%s%.3f\n%s%.3f\n",
      "The average of w and x is ", average( 2, w, x ),
      "The average of w, x, and y is ", average( 3, w, x, y ),
      "The average of w, x, y, and z is ", 
      average( 4, w, x, y, z ) );

   return 0; /* indicates successful termination */

} /* end main */

/* calculate average */
double average( int i, ... )
{ 
   double total = 0; /* initialize total */
   int j; /* counter for selecting arguments  */
   va_list ap; /* stores information needed by va_start and va_end */

   va_start( ap, i ); /* initializes the va_list object */

   /* process variable length argument list */
   for ( j = 1; j <= i; j++ ) {
      total += va_arg( ap, double );
   } /* end for */

   va_end( ap ); /* clean up variable-length argument list */

   return total / i; /* calculate average */
} /* end function average */

 

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