protected static Ptg calcAtanh( Ptg[] operands )
	{
		if( operands.length != 1 )
		{
			return PtgCalculator.getNAError();
		}
		double dd = 0.0;
		try
		{
			dd = operands[0].getDoubleVal();
		}
		catch( NumberFormatException e )
		{
			return PtgCalculator.getValueError();
		}
		if( (dd > 1) || (dd < -1) )
		{
			return PtgCalculator.getError();
		}
		if( new Double( dd ).isNaN() ) // Not a Num -- possibly PtgErr
		{
			return PtgCalculator.getError();
		}

		double res = (0.5 * Math.log( (1.0 + dd) / (1.0 - dd) ));
		PtgNumber ptnum = new PtgNumber( res );
		return ptnum;
	}