/* DEC	*WeightedMean(pDst,pSrc,weight,n)
 *
 * ARGUMENT
 *	DEC	*pDst;
 *	DEC	**pSrc,	**weight;
 *	int n;
 *
 * DESCRIPTION
 *	Sets pDst to the weighted mean of the n	DEC elements
 *   of	the array pSrc[i], each	with weight weight[i].
 *   n <= 0 is not allowed.  pDst is unchanged if an error occurs.
 *
 * SIDE	EFFECTS
 *	None.
 *
 * RETURNS
 *	Returns	pointer	to the average if successful, otherwise
 *   returns GM_NULL.
 *
 * POSSIBLE ERROR CODES
 *
 *	GM_NULLPOINTER
 *	GM_ARGVAL
 *	GM_OVERFLOW
 *	GM_UNDERFLOW
 *
 * AUTHOR
 *	Jared Levy
 *   Copyright (C) 1987-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 */

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

DEC	*WeightedMean(pDst,pSrc,weight,n)
DEC	*pDst;
DEC	**pSrc,	**weight;
int n;
{
	int i;
	DEC	dsum, *sum=&dsum, dsumw, *sumw=&dsumw;
	DEC	dprod, *prod=&dprod;
/*  source must	be supplied !! */
	_MacStart(GM_WMEAN);

	if (!pSrc||!weight) {
		_MacErr(GM_NULLPOINTER);
		_MacRet(GM_NULL);
	}

	if (n<=0)  {
		_MacErr(GM_ARGVAL);
		_MacRet(GM_NULL);
	}

	for (i=0; i<n; i++)  {
		_MacInVarD(pSrc[i]);
		_MacInVarD(weight[i]);
		}

	_MacOutVarD(pDst);

	_MacDZero(sum);
	_MacDZero(sumw);

	for (i=0;i<n;i++)  {
		if (_MulDec80Bit(prod, pSrc[i],	weight[i])==GM_OVERFLOW)  {
			_MacErr(GM_OVERFLOW);
			_MacRet(GM_NULL);
		}
		if (_AddDec80Bit(sum, sum, prod)==GM_OVERFLOW)	{
			_MacErr(GM_OVERFLOW);
			_MacRet(GM_NULL);
		}
		(void) _AddDec80Bit(sumw, sumw,	weight[i]);
	}

	if (_MacIsDecZ(sumw))  {
		_MacErr(GM_DIV0);
		_MacRet(GM_NULL);
	}

	pDst = DivideDecimal(pDst, sum,	sumw);

	_MacRet(pDst);
}