/* DEC	*NetPresentValue(net, flows, nflow, intr)
 *
 * ARGUMENT
 *	DEC	*net, **flows, *intr;
 *	int	nflow;
 *
 * DESCRIPTION
 *	Calculates the net present value of a series of	cash flows.
 *   The nflow cash flows in the array flows are processed at interest
 *   rate intr.	 The net present value,	rounded	to two decimal places,
 *   is	stored in net.
 *
 * SIDE	EFFECTS
 *	None.
 *
 * RETURNS
 *	net if successful, otherwise GM_NULL.
 *
 * POSSIBLE ERRORS
 *	GM_NULLPOINTER
 *	GM_ARGVAL
 *
 * AUTHOR
 *  Jared Levy
 *   Copyright (C) 1988-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 *
 */

#include <stdio.h>
#include "gm.h"
#include "gmsystem.h"

DEC	*NetPresentValue(net, flows, nflow, intr)
DEC	*net, **flows, *intr;
int	nflow;
{
	int	i;
	DEC	dtemp, *temp=&dtemp, dooopi, *ooopi=&dooopi;
	DEC	dtnet, *tnet=&dtnet, dpow, *pow=&dpow;

	_MacStart(GM_NPV);

	if (nflow<0)  {
		_MacErr(GM_ARGVAL);
		_MacRet(GM_NULL);
	}
	_MacInVarD(intr);
	if (!flows||!net)  {
		_MacErr(GM_NULLPOINTER);
		_MacRet(GM_NULL);
	}
	for (i=0;i<nflow;i++)  {
		_MacInVarD(flows[i]);
		}

	if (CompareDecimal(intr,&decMinusHundred)!=1)  {
		_MacErr(GM_ARGVAL);
		_MacRet(GM_NULL);
	}

	_MacDZero(tnet);

	_MacDCopy(temp,	intr);
	temp->dc.id+=2;
	(void) _AddDec80Bit(temp, temp,	&decOne);
	(void) _DivDec80Bit(ooopi, &decOne, temp);

	_MacDCopy(pow, (&decOne));

	for (i=0;i<nflow;i++)  {
		(void) _MulDec80Bit(temp, flows[i], pow);
		(void) _AddDec80Bit(tnet, tnet,	temp);
		(void) _MulDec80Bit(pow, pow, ooopi);
	}

	_ScaleDec80Bit(net, tnet, 2);

	_MacRet(net);
}