// SumOfIntegers.C
// (c) Burt Rosenberg 1996
// This program introduces the use of multiple parameters to a function

#include<iostream.h>

int sumInteger (       // Create the function object
   int sum, int k )     // and two integer objects, initialize the
                        // integer objects.
{
   if ( k==0 ) 
   {
      // the sum has been fully calculated
      return sum ;
   }
   else
   {
      // the sum so far is in sum, add k to it and recurse
      return sumInteger( sum+k, k-1 ) ;
   }
}

void main()
{
   int i ;

   // Get input 
   cout << "Enter i: " ;
   cin >> i ;

   // Check for valid input
   if ( i<0 )
   {
      cout << "Error: i must be positive" << endl ;
      return ;
   }

   // Calculate  and print the sum of integer from 0 to i.
   cout << "Sum is " << sumInteger(0,i) << endl ;

}