// Summing a series

/* 
-------------Problem------------
	Based on page 215 of Koffman & Friedman

-------------Analysis-----------

DATA REQUIREMENTS
  Constants
	None
  Inputs
	n - the number of numbers to be summed (int)
  Outputs
	sum - the sum 1+2+3+..n
FORMULAE
	

--------------Design-------------

INITIAL ALGORITHM
	1. Get n
	2. compute sum
	3. display sum
REFINEMENTS
	2. compute the sum
		IN: int n -- number of numbers
		returns: int sum -- Sigma [i in 1..n] (i)
		Additional variable int i as loop control and 
	   2.1 set sum to 
	   2.2 For i = 1,2,3,...,
	 	  2.2.1 add i to sum

------------Implementation---------
*/

#include <iostream.h>
#include <iomanip.h>

int main( )
{ 
	int n;	//input:  number of numbers
	int sum;//output: sum of numbers
	
	// Uses
	int compute_sum(int);

	//1. Get n
	cout<<"Input a whole number greater than 0: ";
	cin >>n;
	//2. compute sum
	sum=compute_sum(n);
	//3. display sum
	cout<<"Sum 1+2+..+"<<n<<" is "<<sum<<endl;

  return 0; // terminate program with a "zero errors" status returned to UNIX
}

//------------------------------compute_sum-------------------------
int compute_sum(int n)
{
	int sum;
	int i;  // Loop control variable

	// 2.1 set sum to 0 and i to 1
	sum=0;
	
	// 2.2 For i = 1,2,3,4,..n
	for(i=1;  i <= n; ++i);
	{
		//2.2.1 Add i to sum
		sum +=   i;
	}
	return sum;
}