//
// Program:  array_sum
//
// Purpose:  test recursive function for computing sum of 
//   elements of an array.
//
// Input:
//   up to MAXSIZE integers from standard input.  
//   (currently MAXSIZE=50.)
// Output:
//   the sum of the integers entered, printed to standard 
//   output.
//
// Observe that this is *not* the best way to compute the
// sum of some numbers entered from standard input!  the
// point of this program, however, is to demonstrate use
// of recursion.
//

#include <iostream.h>
#include <stdlib.h>		// has EXIT_SUCCESS

// Recursive function to compute sum of array elements.
// Pre:  n >= 0, and array a has at least n elements.
// Post:  returns sum of a[0] .. a[n-1].
int array_sum(int n, int a[])
{
  if (n == 0)
    return 0;
  else
    return a[n-1] + array_sum(n-1, a);
}

// Main program.
int main(void)
{
  const int MAXSIZE = 50;
  int a[MAXSIZE];
  int n;
  cout << "Enter up to " << MAXSIZE << 
    " integers, ctrl-D to end:\n";
  n = 0;
  while ((n < MAXSIZE) && (cin >> a[n])) 
    n++;
  if (n == 0)
    cout << "nothing entered!\n";
  else
    cout << "sum of input integers = " << 
      array_sum(n, a) << endl;
  return EXIT_SUCCESS;
}