[Cfp-interest 1845] Re: C23 vs 754

[Jim Thomas]

> On Nov 3, 2020, at 8:46 AM, Fred J. Tydeman <tydeman at tybor.com> wrote:
> 
> Here are the places that I found where C23 needs to be updated due to IEEE-754.
> 
> 
> ---
> Fred J. Tydeman        Tydeman Consulting
> tydeman at tybor.com <mailto:tydeman at tybor.com>      Testing, numerics, programming
> +1 (702) 608-6093      Vice-chair of PL22.11 (ANSI "C")
> Sample C99+FPCE tests: http://www.tybor.com <http://www.tybor.com/>
> Savers sleep well, investors eat well, spenders work forever.
> 
> 
> Submitter:CFP group
> Submission Date: 2020-??-??
> Document: WG14 N25??
> Title: N25??: C23 versus IEEE 754-2019
> Reference Documents: N2583, IEEE 754-2019
> 
> Summary: There are a few places in C23 that have not caught up with IEEE 754-2019 aka IEC 60559-2020.
> 
> Note to editor: "inf" should be replaced with infinity symbol.
> 
> Add to C23 F.10.4.2 compoundn:
> compoundn(+/-0,n) returns 1
> compoundn(+inf,n) returns +inf for n>0
> compoundn(+inf,n) returns +0 for n<0
> compoundn(NaN,n) returns NaN for n!=0
The case with a NaN argument is covered by F.10 #13: "Functions with a NaN argument return a NaN result and raise no floating-point exception, except where explicitly stated otherwise."
> Add to C23 F.10.4.7 powr:
> powr(x,NaN) returns NaN for 0 <= x.
> powr(NaN,y) returns NaN.
> powr(+1,+/-inf) returns a NaN and raises the "invalid" floating-point exception.
As above, for the cases with NaN arguments.
>     
> Also, remove the line:
> - powr(+1, y)
> F.10.8.1 copysign
> Change
> 
> copysign is specified in the Appendix to IEC 60559.
> to
> copysign is specified in the Appendix to IEC 60559.
This line can be omitted, because copySign is an IEC 60559 standard operation now and the binding is given in the first table in F.3.

- Jim Thomas

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