/* DEC	*Median(pDst,pSrc,n)
 *
 * ARGUMENT
 *	DEC	*pDst;
 *	DEC	**pSrc;
 *	int n;
 *
 * DESCRIPTION
 *	Sets pDst to the median	of the n DEC elements of the array pSrc.
 *   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_NOMEMORY
 *
 * AUTHOR
 *	Jared Levy
 *   Copyright (C) 1987-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 */

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

DEC	*Median(pDst,pSrc,n)
DEC	*pDst;
DEC	**pSrc;
int	n;
{
	int	i;
	DEC	**tmpa,	dsum, *sum=&dsum;
	extern void qsort(char *, unsigned, unsigned, int (*)(void));

	_MacStart(GM_MEDIAN);

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

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

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

	_MacOutVarD(pDst);

	/* allocate array of pointers */
	tmpa = (DEC **)	calloc(n, sizeof(DEC *));
	if (!tmpa)  {
		_MacErr(GM_NOMEMORY);
		_MacRet(GM_NULL);
	}

	/* copy	pointers */
	for (i=0;i<n;i++)
		tmpa[i]	= pSrc[i];

	/* sort	pointers */
	qsort((void *)tmpa,n,sizeof(DEC	*), _SortInc);

	if (n%2)
		_MacDCopy(pDst,	tmpa[(n-1)/2]);
	else  {
		(void) _AddDec80Bit(sum, tmpa[n/2-1], tmpa[n/2]);
		MultiplyDecimal(pDst, sum, &decPoint5);
	}

	free ((char *) tmpa);

	_MacRet(pDst);
}