Re: [boost] [serialization] facets for non-finite numbers

From: Robert Ramey (ramey_at_[hidden])
Date: 2006-08-01 10:56:39

Paul A Bristow wrote:
> For the record, as a punishment for raising this issue at the UK C++
> BSI group meeting, I was tasked with raising the issue for the C++
> Standards group.
>
> Some rambling thoughts on this issue are at
>
> http://www2.open-std.org/JTC1/SC22/WG21/docs/papers/2006/n2022.pdf
>
> Your implementation almost certainly provides a 'proof_of_concept'
> for this - as if it was needed.
>
> And I suspect more than a few will be well advised to use it -
> otherwise
> they may find to their cost (possibly considerable cost) that some
> archives turn out to be not readable because some floating-point
> calculation has produced an infinity or NaN.
>
> If you don't do this, it would seem prudent to ensure that every
> floating-point serialized is checked for finiteness before writing to
> the archive, and worrying about what to do it any are not!

So what is needed is a "companion" facet which traps attempts
to write NaNs and throws an exception.  Usage of one or the
other of these facets would eliminate undefined behavior.

Robert Ramey

>
> Thanks.
>
> Paul
>
> ---
> Paul A Bristow
> Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB
> [phone] & SMS, Mobile [phone] & SMS
> pbristow_at_[hidden]
>
>
>
>
>
>>  -----Original Message-----
>>  From: boost-bounces_at_[hidden]
>>  [mailto:boost-bounces_at_[hidden]] On Behalf Of Johan Råde
>>  Sent: 30 July 2006 11:02
>>  To: boost_at_[hidden]
>>  Subject: Re: [boost] [serialization] facets for non-finite numbers
>>
>>  Robert Ramey wrote:
>>  > Johan Råde wrote:
>>  >> Johan Råde wrote:
>>  >>> At the suggestion of Robert Ramey's, I have put together
>>  facets for
>>  >>> reading and writing non-finite numbers, such as infinity and
>>  >>> not-a-number, to text streams, in a consistent and portable way.
>>  >>>
>>  >>> If there is enough interest in the code, I will submit it for a
>>  >>> mini-review, in order to have it added to the serialization lib.
>>  >>>
>>  >
>>  > Actually, I would like the other codecvt facets in boost
>>  be promoted
>>  > to official status.  There should be a "place" in boost
>>  for these and
>>  > other facets.
>>  >
>>  > Robert Ramey
>>  >
>>  >
>>  >>> --Johan Råde
>>  >>
>>  >> New version uploaded to the vault,
>>  >> serialization/non_finite_num_facets.zip. This version has:
>>  >>
>>  >> 1. better handling of fomatting flags
>>  >> 2. more robust check for not-a-number
>>  >> 3. more tests
>>  >> 4. some minor issues have been fixed
>>  >> 5. various code improvements
>>  >>
>>  >> Now I'm not going to make any more changes for a while.
>>  >> Got other things to do.
>>  >>
>>  >> --Johan Råde
>>  >>
>>  >> _______________________________________________
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>>  >
>>  >
>>  >
>>  >
>>  -------------------------------------------------------------
>>  -----------
>>  >
>>  > _______________________________________________
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>>
>>  I think there should be a Boost facets library,
>>  with the UTF-8 codecvt facet and my non-finite number facets.
>>  There is no reason why they should be buried in the
>>  serialization library.
>>
>>  But I'm not the right person to take care of that.
>>  My area is scientific computing and GUI programming,
>>  and I know almost nothing about locales, facets and
>>  internationalization.
>>
>>  --Johan Råde
>>
>>
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