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

[huizhe wang]

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
>>
>