roundTiesToEven

Brendan Eich brendan at mozilla.org
Sun Nov 11 11:22:24 PST 2007


On Nov 11, 2007, at 4:11 AM, liorean wrote:

> On 11/11/2007, Jonathan Watt <jwatt at jwatt.org> wrote:
>> I've noticed that rounding in the reference implementation is  
>> implemented using
>> IEEE roundTiesToEven, but in browsers .5 values appear to round  
>> towards zero.
>> Although roundTiesToEven is desirable from a computational point  
>> of view,
>> there's likely a significant risk that changing to this method  
>> could break some
>> existing ECMAScript.
>
> That's really serious breakage - books, tutorials, references and real
> world code all take for granted that halves alway round up.

Don't worry, that's not an intended change to double rounding  
(decimal is new and has more rounding control, but for double we're  
stuck).

It looks like an unintended consequence of using the SML-NJ Real64  
library. I filed http://bugs.ecmascript.org/ticket/301. Thanks,  
Jonathan, for pointing this out,

/be




More information about the Es4-discuss mailing list