/* DEC	*Factorial(pDst, n)
 *
 * ARGUMENT
 *	DEC	*pDst;
 *	unsigned n;
 *
 * DESCRIPTION
 *	Sets pDst = n!
 *
 * SIDE	EFFECTS
 *	None.
 *
 * RETURNS
 *	pDst if	successful, GM_NULL otherwise
 *
 * POSSIBLE ERRORS
 *	GM_NOMEMORY
 *	GM_OVERFLOW  (if n > 20)
 *
 * AUTHOR
 *  Jared Levy
 *   Copyright (C) 1987-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 *
 */

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

DEC	*Factorial(pDst, n)
DEC	*pDst;
unsigned n;
{
	DEC	dmult, *mult = &dmult;
	unsigned	i;

	_MacStart(GM_DFACT);

	_MacOutVarD(pDst);

/* check for overflow */
	if (n >	20)  {
		_MacErr(GM_OVERFLOW);
		_MacRet(GM_NULL);
	}

/* do calculations */
	_MacDCopy(pDst,	&decOne);
	_MacDCopy(mult,	&decOne);

	for (i=2; i<=n;	i++)  {
		mult->dc.sl[0] = i;
		_MulDec80Bit(pDst, pDst, mult);
	}

/* pDst	fits into 64 bits */
	_MacRet(pDst);
}