[Cfp-interest] C binding for IEEE 754-2008

[Jim Thomas]

On Jul 18, 2012, at 3:49 AM, Dan Zuras IEEE wrote:

>> From: Jim Thomas <jaswthomas at sbcglobal.net>
>> Subject: C binding for IEEE 754-2008
>> Date: Mon, 16 Jul 2012 16:56:04 -0700
>> Cc: CFP <cfp-interest at ucbtest.org>, John Benito <benito at bluepilot.com>
>> To: stds-754 at IEEE.ORG
>> 
>> 
>> A C floating point study group, under ISO/IEC JTC1/SC22/WG14, the =
>> international standardization working group for the programming language =
>> C, has been working on a C language binding for IEEE Std 754-2008. WG14 =
>> is currently seeking approval to adopt this specification as a work =
>> item. A draft of Part 1 of the specification is posted at =
>> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1615.pdf for early =
>> informal review. Your review and input would be much appreciated. Please =
>> send comments to the study group reflector at cfp-interest at ucbtest.org.
>> 
>> -Jim Thomas=
> 
> 	Jim,
> 
> 	(From just a few cursory readings.)
> 
> 	I see almost no mention of either the newly defined
> 	tower of precisions or the elements of Clause 9 other
> 	than their mention WRT rounding modes.  Although it
> 	mentions that these will appear in parts 3 through 5.
> 
> 	While I recognise that both the tower & transcendental
> 	functions are optional, not specifying them for C means
> 	that C (likely) never intendeds to support them.
> 
> 	If this is so it should be stated up front.  Or, if it
> 	is intended that they be supported in some later
> 	revision of C, that should be stated.
> 
> 	While it is mentioned (up front) that 754 went to a
> 	lot of trouble to support intelligent reproducibility,
> 	there seems to be less support of it within C.  Same
> 	comments as above.  (Or are these in part 5?)
> 
> 	I notice that support of those things that will lead
> 	to the support of intervals is also not mentioned
> 	even though we went to some trouble to put them in
> 	754.  As there is a committee currently working on
> 	the interval standard (1788), I consider this as
> 	largely justified on that basis alone.
> 
> 	The rest seems just fine to me on a cursory look.
> 
> 	Enjoy,
> 
> 				Dan

Dan,

Thanks for the comments.

As the introduction says, the study group plans to provide the 754 binding for C in a Technical Specification in five Parts. What's posted for informal review is just the first Part. The tower of precision will be included in Part 3 (Interchange and extended types), the Clause 9 elements in Part 4 (Supplemental functions). Reproducible results would fit in Part 5 (Supplemental attributes).

Note that all of this is first intended to become an ISO/IEC Technical Specification. Each Part, assuming it makes it through the approval process, will have well-defined conformance, which a C implementation may support. A future revision of the C standard may include some or all of the TS.

-Jim