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Re: possible decision on interchange representation



John, Michel, Dima, P-1788,

See my appended comment.

Baker

On 06/19/2014 06:03 AM, John Pryce wrote:
Michel
(and Dmitry, Baker)

On 2014 Jun 18, at 14:28, Michel Hack wrote:
(John wrote:)
Am I missing something crucial here?

Yes!  Namely the fact that Endianness is defined for individual typed
fields, such as int16, int32, int64, float, double, etc. -- and not for
aggregates.  No too long ago, especially for non-IEEE floating-point
formats, the rules were much messier than simple byte reversal, as for
example bytes reversed in pairs within the representation.

So we CAN define the interval interchange format as suggested in C6.2,
and apparently as originally intended, namely as an ordered triple of
standard objects, each object being represented at Level 4 in its usual
format for the platform.  This does not resolve portability issues due
to differing Endianness, but it reduces them to the same problem faced
by almost every other interchange format...

I think you and Dmitry should work this out between you and produce the revised wording.

Baker, as it is substantive, does it need a separate motion?


I suggest Dima and Michel should discuss this.  I DO see an additional
decision here we should be pondering, namely, do we want to:

1. specify the bit order completely in the interchange format,
   thus ensuring portability at the expense of favoring some
   manufacturers over others (strong standard),

2. not specify the endian-ness of the binary components of the
   interchange format, thus being equal-handed with regard
   to present architectures (weaker standard), or

3. something else (specifying order of chunks, as Michel has
   described)?

Let's see what Dima and Michel come up with, and go from there.
(I'm hoping we can hand over the document soon with time for a
sponsor ballot, but only if the document is high-enough quality
and does what we want.)

Best regards,

Baker


--

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Ralph Baker Kearfott,   rbk@xxxxxxxxxxxxx   (337) 482-5346 (fax)
(337) 482-5270 (work)                     (337) 993-1827 (home)
URL: http://interval.louisiana.edu/kearfott.html
Department of Mathematics, University of Louisiana at Lafayette
(Room 217 Maxim D. Doucet Hall, 1403 Johnston Street)
Box 4-1010, Lafayette, LA 70504-1010, USA
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