RFR 8015978: Incorrect transformation of XPath expression "string(-0)"

[Joe Darcy]

Hello Aleksej,

Looking at the code, I have another suggestion. If this code can run 
exclusively on JDK 8 or later, replace

  955             if (Double.isNaN(d) || Double.isInfinite(d))
  956                 return(Double.toString(d));

with

  955             if (!Double.isFinite(d))
  956                 return(Double.toString(d));

Cheers,

-Joe

On 6/9/2013 11:18 AM, Aleksej Efimov wrote:
> Joe,
>
> I definitely like it:
> 1. Its a one-line change - perfect size.
> 2. Its fastest one from discussed previously.
> 3. -0.0 -> 0.0 has tests.
> 4. And it solves our problem.
>
> As a result of all props the next version of webrev: 
> http://cr.openjdk.java.net/~coffeys/webrev.8015978.v2/ 
> <http://cr.openjdk.java.net/%7Ecoffeys/webrev.8015978.v2/>
>
> Thanks
> -Aleksej
>
> On 06/07/2013 11:11 PM, huizhe wang wrote:
>> Nice. One-line change, I guess Aleksej would love it :-)
>>
>> On 6/7/2013 10:19 AM, Joe Darcy wrote:
>>> I'll do you one better; you can turn a negative zero into a positive 
>>> zero leaving other values unchanged like this:
>>>
>>>     d = d + 0.0;
>>>
>>> In IEEE 754 under the round-to-nearest-even rounding mode required 
>>> by Java
>>>     -0.0 + 0.0 => (+)0.0
>>>
>>> This trick is used in various places in Java's numerical libraries, 
>>> is required behavior by our specifications, and even has some tests 
>>> for it :-)
>>>
>>> -Joe
>>>
>>> On 6/7/2013 8:43 AM, David Chase wrote:
>>>> Wouldn't be more efficient to do the following, assuming that the 
>>>> full Java compilation chain respects the trickiness of 0 vs -0:
>>>>
>>>>     if (d == 0.0) {
>>>>          d=0.0 // Jam -0 == +0 to +0, per 
>>>> http://www.w3.org/TR/xpath/#function-string
>>>>
>>>>     }
>>>>
>>>> Division's plenty more expensive than assigning a constant, 
>>>> especially on platforms that lack hardware FP division.
>>>>
>>>> David
>>>>
>>>> On 2013-06-07, at 2:03 AM, huizhe wang <huizhe.wang at oracle.com> wrote:
>>>>
>>>>> Hi Aleksej,
>>>>>
>>>>> According to XPath spec, both positive and negative zero are 
>>>>> converted to the string 0, so it seems doesn't matter. But if you 
>>>>> want to detect the negative zero, you may do the following:
>>>>>     if (d == 0.0 && 1/d < 0.0) {
>>>>>          d=0.0
>>>>>     }
>>>>>
>>>>> Recognizing that (-0.0 == 0.0), and (1/(-0.0) == -Infinity).
>>>>>
>>>>> -Joe
>>>>
>>>
>>
>