protected static Ptg calcType( Ptg[] operands )
	{
		if( operands[0] instanceof PtgArray )
		{
			return new PtgNumber( 64 );    // avoid value calc for arrays
		}
		if( operands[0] instanceof PtgErr )
		{
			return new PtgNumber( 16 );
		}

		// otherwise, test value of operand
		Object value = operands[0].getValue();
		int type = 0;
		if( value instanceof String )
		{
			type = 2;
		}
		else if( value instanceof Number )
		{
			type = 1;
		}
		else if( value instanceof Boolean )
		{
			type = 4;
		}
		return new PtgNumber( type );
	}