/* DEC	*PowerRational(pDst,pSrc1,m,n)
 *
 * ARGUMENT
 *	DEC	*pDst,*pSrc1;
 *	int	m,n;
 *
 * DESCRIPTION
 *	Calculates pSrc1 to the	power m/n and returns the answer in pDst.
 *  This provides an x**(m/n) power function for DEC numbers.
 *
 * SIDE	EFFECTS
 *	None.
 *
 * RETURNS
 *	Pointer	to the result if no error, otherwise GM_NULL.
 *
 * ALGORITHM:
 *	x**(m/n) = e**((m/n)*ln(x)). Therefore,	call dlnx() to get the
 *	natural	log
 *  and	then multiply by the power of x.  Finally, call	dexx() to provide
 *  e**z.
 *
 * POSSIBLE ERROR CODES
 *
 *	GM_NULLPOINTER
 *	GM_OVERFLOW
 *	GM_UNDERFLOW
 *	GM_IMAG
 *	GM_PWR0
 *	GM_DIV0
 *
 * AUTHOR
 *  Andy Anderson   05-JAN-1987	 17:30
 *   Copyright (C) 1987-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 */

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

DEC	*PowerRational(pDst,pSrc,m,n)
DEC	*pDst, *pSrc;
int	m,n;
{
	DEC	temp, *pt, *nsrc, dnsrc, ddm, *dm=&ddm;
	int	i, isn=0;

	_MacStart(GM_DPOWRAT);
	_MacInVarD(pSrc);
	_MacOutVarD(pDst);

	if (n == 0)  {
		_MacErr(GM_DIV0);
		_MacRet(GM_NULL);
	}

	if (_MacIsDecZ(pSrc))  {
		if (!((m<0)^(n<0))&&(m!=0))  {
			_MacDZero(pDst);
			_MacRet(pDst);
		}
		else  {
			_MacErr(GM_PWR0);
			_MacRet(GM_NULL);
		}
	}

	if (m == 0)  {
		_MacDCopy(pDst,&decOne);
		_MacRet(pDst);
	}

	if (_MacIsDecN(pSrc))  {
		while ((m % 2) + (n % 2) == 0)	{
			m=m/2;
			n=n/2;
		}
		if ((n % 2) == 0)  {
			_MacErr(GM_IMAG);
			_MacRet(GM_NULL);
		}
		isn=m %	2;
		nsrc = &dnsrc;
		_MacDCopy(nsrc,pSrc);
		pSrc=nsrc;
		_MacDChgs(nsrc);
	}

	pt = &temp;

	(void) _LnDec80Bit(pt, pSrc);

	(void) ConvLongToDecimal(dm, (long) m);
	(void) _MulDec80Bit(pt,	pt, dm);

	(void) ConvLongToDecimal(dm, (long) n);
	(void) _DivDec80Bit(pt,	pt, dm);

	i = _ExpDec80Bit(pt, pt);
	if(i==GM_OVERFLOW) {
		_MacErr(i);
		_MacRet(GM_NULL);
		}

	i = _Sq5UnsTo4Uns(pt);
	if(i!=GM_SUCCESS) {
		_MacErr(GM_OVERFLOW);
		_MacRet(GM_NULL);
	}

	if (_MacIsDecZ(pt))  {
		_MacErr(GM_UNDERFLOW);
	}

	if (isn)
		_MacDChgs(pt);

	_MacDCopy(pDst,pt);
	_MacRet(pDst);
}