like7.c

    *hist_size = sslot.nvalues;
		if (sslot.nvalues >= min_hist_size)
		{
			int			nmatch = 0;
			int			i;

			for (i = n_skip; i < sslot.nvalues - n_skip; i++)
			{
				if (varonleft ?
					DatumGetBool(FunctionCall2Coll(opproc,
												   sslot.stacoll,
												   sslot.values[i],
												   constval)) :
					DatumGetBool(FunctionCall2Coll(opproc,
												   sslot.stacoll,
												   constval,
												   sslot.values[i])))
					nmatch++;
			}
			result = ((double) nmatch) / ((double) (sslot.nvalues - 2 * n_skip));