@Description("natural logarithm")
    @ScalarFunction
    @SqlType(StandardTypes.DOUBLE)
    public static double ln(@SqlType(StandardTypes.DOUBLE) double num)
    {
        return Math.log(num);
    }
@Test
    public void testLn()
    {
        for (double doubleValue : DOUBLE_VALUES) {
            assertFunction("ln(" + doubleValue + ")", DOUBLE, Math.log(doubleValue));
        }
        assertFunction("ln(NULL)", DOUBLE, null);
    }