/* DEC	**DepreciateStraightLineTable(depr,remval, book, salv, life, partial);
 *
 * ARGUMENT
 *	DEC	**depr,	**remval, *book, *salv,	*partial;
 *	int	life;
 *
 * DESCRIPTION
 *	Calculate several years' depreciation and remaining depreciable
 *   value according to	straight line depreciation.  The item has book value
 *   book, salvage value salv, and lifetime life (which	may include a partial
 *   period).  At year#	i, the depreciation and	remaining value	are
 *   computed and stored in depr[i] and	remval[i].  The	first year is always
 *   the partial year.	The results are	calculated for the entire lifetime.
 *
 * SIDE	EFFECTS
 *	depr and remval	are changed.
 *
 * RETURNS
 *	depr if	successful, otherwise GM_NULLARR.
 *
 * 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	**DepreciateStraightLineTable(depr, remval, book, salv,	life, partial)
DEC	**depr,	**remval, *book, *salv,	*partial;
int	life;
{
	int	i, plife;
	DEC	dtotlif, *totlif=&dtotlif;
	DEC	dydep, *ydep=&dydep;

	_MacStart(GM_DPSLTBL);

	if (!depr||!remval||!book||!salv||!partial)  {
		_MacErr(GM_NULLPOINTER);
		_MacRet(GM_NULLARR);
	}
	if (_MacBad(book)||_MacBad(salv)||_MacBad(partial))  {
		_MacErr(GM_INIT);
		_MacRet(GM_NULLARR);
	}

	plife=life+(_MacIsDecZ(partial)?0:1);

	for (i=0;i<=plife;i++)
		if(!depr[i]||!remval[i])  {
			_MacErr(GM_NULLPOINTER);
			_MacRet(GM_NULLARR);
		}

/* check life>=1, 0<=partial<=1	*/
	if (life<1||_MacIsDecN(partial)||CompareDecimal(partial,&decOne)==1
		||_MacIsDecN(book)||_MacIsDecN(salv))  {
		_MacErr(GM_ARGVAL);
		_MacRet(GM_NULLARR);
	}

/* calculate yearly depreciation */
	(void) _SubDec80Bit(remval[0],book,salv);
	(void) _ScaleDec80Bit(remval[0], remval[0], 2);
	(void) ConvLongToDecimal(totlif, (long)	life);
	(void) _DivRndDec80Bit(ydep, remval[0],	totlif,	2);

	_MacDZero(depr[0]);

/* handle partial first	year */
	if (_MacIsDecZ(partial))  {
		i=0;
	}
	else  {
		(void) _MulDec80Bit(depr[1],ydep,partial);
		(void) _ScaleDec80Bit(depr[1],depr[1],2);
		(void) _SubDec80Bit(remval[1], remval[0], depr[1]);
		i=1;
	}

/* handle remaining years */

	while (i<plife)	 {
		i++;
		_MacDCopy(depr[i],ydep);
		(void) _SubDec80Bit(remval[i], remval[i-1], ydep);
	}

/* add balance to last depreciation period */
	_MacDCopy(depr[plife],remval[plife-1]);
	_MacDZero(remval[plife]);

	_MacRet(depr);
}