[Cfp-interest 1706] Re: Decimal math functions paper

[Jim Thomas]

Wasn’t this dealt with in N 2359 which is listed in N 2478 as one of the changes that have been applied to the C2X draft?

- Jim Thomas

> On Jul 20, 2020, at 12:49 PM, Fred J. Tydeman <tydeman at tybor.com> wrote:
> 
> Attached
> 
> 
> ---
> 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")
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> 
> 
> Submitter:Fred J. Tydeman
> Submission Date: 2020-mm-dd
> Document: WG14 N2xxx
> Title: N2xxx: Decimal math functions
> Reference Documents: N1949, N2355, N2377, N2309, N2401, N2451, N2478
> 
> Summary: The decimal math functions need more __STDC_ #define's to be usable.
> 
> Decimal floating-point is optional (N2478 6.10.8.3 Conditional feature macros):
> 
> __STDC_IEC_60559_DFP__ The integer constant yyyymmL, intended to indicate support of decimal floating types and conformance to Annex F for IEC 60559 decimal floating-point arithmetic.
> 
> and Annex F IEC 60559 floating-point arithmetic:
> 
> An implementation that defines __STDC_IEC_60559_DFP__ to yyyymmL shall conform to the specifications for decimal floating-point arithmetic in the following subclauses of this annex: ....
> 
> Therefore, any use of a decimal facility (such as _Decimal64) would need to be enclosed in #ifdef __STDC_IEC_60559_DFP__ ... #endif.
> 
> Are the TS 18661-4, Part 4a supplementary math functions optional?
> 
> N1949 is TS 18661-4 for publication. Later, for C2X, it was broken up into parts.
> 
> N2355 [C11 version] was voted in 2019 May meeting (London)[N2377 minutes]. Along with N2309 [rootn bug fix]. However, N2355 is not a set of detailed changes to C2X.
> 
> N2401 [C17 version] 2019 October meeting (Ithaca)[N2451 minutes] has the detailed updates to C2X. In part, it has:
> 
>  2 Conformance
>    c) it defines __STDC_IEC_60559_FUNCS__ to 201506L.
> However, that macro is not mentioned as a change to C2X in N2401; it was mentioned as a change to 6.10.8.3#1 in N1949.
> 
> I believe that, to get the decimal part 4a math functions, the implementation needs two things.
> 
> 
>  #define __STDC_IEC_60559_DFP__
>  #define __STDC_IEC_60559_FUNCS__
> 
> Also, the user needs two things (as mentioned in N1949):
> 
> 
>  #define __STDC_WANT_IEC_60559_DFP_EXT__
>  #define __STDC_WANT_IEC_60559_FUNCS_EXT__
> 
>     
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