// Fig. E.2: figE_02.cpp
// Using variable-length argument lists.
#include <iostream>
using std::cout;
using std::endl;
using std::ios;

#include <iomanip>
using std::setw;
using std::setprecision;
using std::setiosflags;
using std::fixed;

#include <cstdarg>
using std::va_list;

double average( int, ... );

int main()
{
   double double1 = 37.5;
   double double2 = 22.5;
   double double3 = 1.7;
   double double4 = 10.2;

   cout << fixed << setprecision( 1 ) << "double1 = " 
        << double1 << "\ndouble2 = " << double2 << "\ndouble3 = "
        << double3 << "\ndouble4 = " << double4 << endl
        << setprecision( 3 ) 
        << "\nThe average of double1 and double2 is " 
        << average( 2, double1, double2 )
        << "\nThe average of double1, double2, and double3 is " 
        << average( 3, double1, double2, double3 ) 
        << "\nThe average of double1, double2, double3"
        << " and double4 is " 
        << average( 4, double1, double2, double3, double4 ) 
        << endl;
   return 0;
}  // end main

// calculate average
double average( int count, ... )
{
   double total = 0;
   va_list list;  // for storing information needed by va_start
 
   va_start( list, count );

   // process variable-length argument list
   for ( int i = 1; i <= count; i++ )
      total += va_arg( list, double );

   va_end( list ); // end the va_start
   return total / count;
}  // end function average

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