Thread: qsort question

Hello all -

Is there any way to pass a parameter to the comparison function with qsort without using a global variable?

My goal is to sort the rows of a 2-D matrix based on a particular column. I have a working version that does use globals:

Code:

static int nSortColumn = 0; /* global column index used by sortrows */
void sortrows(double** pMatrix,int nStartRow, int nStopRow, int nColumn)
{
	nSortColumn = nColumn;
	qsort((void*) (pMatrix+nStartRow),nStopRow-nStartRow+1,sizeof(double*),&sortrowsCompareFcn);
}

int sortrowsCompareFcn(const void * a,const void * b)
{
	double** val1 = (double**) a;
	double** val2 = (double**) b;

	if(val1[0][nSortColumn] < val2[0][nSortColumn]  )
	{
		return -1;
	}
	else if(val1[0][nSortColumn] > val2[0][nSortColumn]  )
	{
		return 1;
	}
	else
	{
		return 0;
	}
}

Is a better way to tell the comparison function which column to sort by?

Thanks!