[cfp-interest 3620] Re: Rounding Mode

[Jim Thomas]

Rounding precision mode is in 754-1985, but not in later versions. The attention to rounding precision mode was added to C99 which was designed to support 754-1985. Since 754 no longer mentions rounding precision mode (and assuming the current revision is unlikely to restore it as a feature), why should we elevate its status in C2Y? Just mentioning it as a possible extension, as in footnote 438 in F.8.1, seems appropriate. 

F.8.3 and F.8.4 incorrectly imply that rounding precision mode is an optional feature of ISO/IEC 60559. (Likewise, “trapping” is no longer mentioned as a user feature in 754. Traps are mentioned only in an implementation note.) We might consider updating F.8.3. and F.8.4 to remove the reference to rounding precision (and trapping) mode which is obsolete from a standards perspective. Choosing terms specifically to accommodate rounding precision mode doesn’t seem needed. This is not to suggest what terms should be used.

- Jim Thomas

> On Sep 22, 2025, at 9:03 PM, Damian McGuckin <damianm at esi.com.au> wrote:
> 
> On Mon, 22 Sep 2025, David Hough CFP wrote:
> 
>> I would agree that "rounding mode" is appropriate for statements that apply
>> both to rounding direction and to rounding precision (if available).
>> 
>> Statements that apply to just one or the other need to be appropriately
>> qualified.
> 
> Very wise reply. Your middle name must be Solomon. Got it.
> 
> In most cases, the use of "rounding mode" is only talking about the "rounding direction mode".
> 
> Thanks - Damian
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