/* DEC *BondYield(yield, price,	coupon,	ppy, mop, dap, yrp, mom, dam, yrm)
 *
 * ARGUMENT
 *	DEC	*price;
 *	DEC	*yield;
 *	DEC	*coupon;
 *	int	ppy;
 *	int	mop, dap, yrp;
 *	int	mom, dam, yrm;
 *
 * DESCRIPTION
 *	Calculate the yield of a bond given the	price, coupon rate
 *  for	receiving interest on a	bond, number of	payments per year, and the
 *  puchase and	maturity dates.
 *
 * SIDE	EFFECTS
 *	None.
 *
 * RETURNS
 *	yield if successful, otherwise GM_NULL
 *
 * POSSIBLE ERRORS
 *	GM_NULLPOINTER
 *	GM_INIT
 *	GM_ARGVAL
 *
 * AUTHOR
 *  Jared Levy
 *   Copyright (C) 1988-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 * Mark	Nelson
 *   Added one line to convert nominal interest	rate to	effective.
 *
 */

#include <stdio.h>
#include "gmsystem.h"
DEC	*BondYield(yield, price, coupon, ppy, mop, dap,	yrp, mom, dam, yrm)
DEC	*price,	*yield,	*coupon;
int	ppy, mop, dap, yrp, mom, dam, yrm;
{
	DEC	dtemp, *temp=&dtemp, dtemp2, *temp2=&dtemp2;
	DEC	dnper, *nper=&dnper, dpmt, *pmt=&dpmt;
	DEC	dpv, *pv=&dpv, dfv, *fv=&dfv, *p;
	DEC	ddsc, *dsc=&ddsc, ddcs,	*dcs=&ddcs;
	int	ndays, npay;

	_MacStart(GM_BONDYLD);

	_MacInVarD(coupon);
	_MacInVarD(price);
	_MacOutVarD(yield);

	if (ppy<1||ppy>12)  {
		_MacErr(GM_ARGVAL);
		_MacRet(GM_NULL);
	}

	/* calculate # of periods, including partial period */
	ndays =	DaysBetweenDates360(mom, dam, yrm, mop,	dap, yrp);
	if (ndays < 0)	{
		if (ndays!=GM_ARGVAL&&ndays!=GM_OVERFLOW)
			_MacErr(GM_ARGVAL);
		_MacRet(GM_NULL);
	}

	/* calculate number of interest	payments remaining */
	(void) ConvLongToDecimal(temp, (long)ppy * (long) ndays);
	(void) ConvLongToDecimal(temp2,	 360L);
	(void) _DivDec80Bit(nper, temp,	temp2);

	(void) _TruncateDec80Bit(temp, nper, 0);
	npay=temp->dc.sl[0];
	(void) _SubDec80Bit(dsc, nper, temp);	/* days	purchase - next	int */
	(void) _SubDec80Bit(dcs, &decOne, dsc);	/* days	last int - purchass */

	/* calculate coupon rate per period */
	(void) ConvLongToDecimal(temp2,	(long)ppy);
	(void) _DivDec80Bit(pmt, coupon, temp2);

	(void) _AddDec80Bit(fv,	&decHundred, pmt);

	(void) _MulDec80Bit(temp, pmt, dcs);
	(void) _AddDec80Bit(pv,	price, temp);

	if (CompareDecimal(nper, &decOne)<=0)  {  /* < 1 period	to maturity */
		_DivDec80Bit(temp, fv, pv);
		_SubDec80Bit(temp, temp, &decOne);
		_DivDec80Bit(yield, temp, dsc);
		_MulDec80Bit(yield, yield, &decHundred);
		_ScaleDec80Bit(yield, yield, wIntrPrec);
	}
	else  {					  /* > 1 period	to maturity */
		_MacDChgs(pv);
		p = _InterestAux(3, npay, dsc, yield, pv, pmt, fv, GM_BEGIN);
		if (!p)
			_MacRet(GM_NULL);
	}
/*
 * At this point, yield	contains the nominal interest rate for the bond.
 * This	needs to be converted to the effective interest	rate.  Rather than
 * call	the NominalToEffective routine,	I import most of the code.
 */
	yield->dc.id +=	2;
	_AddDec80Bit( yield, yield, &decOne );
	if (_IntPwrDec80Bit( yield, yield, ppy ) != GM_SUCCESS ) {
	    _MacErr( GM_ARGVAL );
	    _MacRet( GM_NULL );
	}
	_SubDec80Bit( yield, yield, &decOne );
	if (yield->dc.id >= GM_MINID+2)
		yield->dc.id -=	2;
	else
		(void) _MulUnsArrByPwrOf10(yield->dc.sl, 5, 2);
	if (_Sq5UnsTo4Uns(yield)!=GM_SUCCESS)  {
		_MacErr(GM_ARGVAL);
		_MacRet(GM_NULL);
	}
	_MacRet(yield);
}