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

[Jim Thomas]

Michel,

Thanks for the comments. Please see responses below.

-Jim

On Jul 18, 2012, at 1:00 PM, Michel Hack wrote:

> Dan Zuras wrote:
>> 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.
> 
> Well, at least they *are* mentioned.
> 
> It would indeed be nice if a language like C could provide
> for a class of precisions not just for FP, but also for
> integer variables, to allow a compiler to synthesize the
> appropriate platform-specific arbitrary-precision idioms
> instead of each programmer having to invent their own,
> less portable, implementations.

Part 3 of the CFP TS will specify the 754 precisions for FP. I think integer types are out of scope for our study group. What do you think is needed beyond <stdint.h> and <inttypes.h>?

> 
> I like the way sensible support for NaNs is finally being
> introduced -- in particular the payload functions, which
> may finally allow reasonably-portable code to be written,
> and enable some of the decoration encodings we have been
> discussing in stds-1788 for compressed intervals.

Good to hear.

> 
> One thing I missed was recommendations (if not mandates)
> for payload preservation across casts.  Perhaps that would
> be addressed in Part 3, which may address cross-radix casts.

These recommendations can be considered part of 754 operation semantics which are adopted by reference by the TS. Maybe an explicit mention would be helpful.

> 
> I also like the way conversions to and from strings have
> been described -- and am glad that the rules were interpreted
> the same way I did when I brought the AIX conversion routines
> into 754-2008 conformance.

Very good.

> 
> Michel.
> ---Sent: 2012-07-18 20:06:31 UTC
> 
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