[Cfp-interest 2489] Re: 5.2.4.2.3 and IEC 60559

[Jim Thomas]

The decimal floating types are IEC 60559 decimal formats.

The characteristics if 5.2.4.2.3 are given the specific values for IEC 60559 decimal formats, rather than limits as in 5.2.4.2.2.

6.2.5#12 says "There are three decimal floating types, designated as _Decimal32, _Decimal64, and _Decimal128.
Respectively, they have the IEC 60559 formats: decimal32,48) decimal64, and decimal128.” 

6.3.1.4 says “Decimal floating-point operations and IEC 60559 binary floating-point operations (Annex F) access
the same floating-point exception status flags.”

6.3.1.5 says "When a value of real floating type is converted to a decimal floating type, if the value being converted
cannot be represented exactly, the result is correctly rounded with exceptions raised as specified in IEC 60559."

6.5#9 says "Operators involving decimal floating types are evaluated according to the semantics of IEC 60559,
including production of results with the preferred quantum exponent as specified in IEC 60559.”

6.10.9.3#1 says "__STDC_IEC_60559_DFP__ The integer constant 202311L, intended to indicate support of decimal
floating types and conformance to Annex F (IEC 60559 floating-point arithmetic) for decimal floating-point arithmetic.” Decimal floating-point functions in 7.12 are guarded by #ifdef __STDC_IEC_60559_DFP__.

7.6 says  "Decimal floating-point operations and IEC 60559 binary floating-point operations (Annex F) access
the same floating-point exception status flags.”

- Jim Thomas

> On Aug 1, 2022, at 8:46 PM, Fred J. Tydeman <tydeman at tybor.com> wrote:
> 
> It appears to me that section 5.2.4.2.3 assumes that decimal floating point (DFP) is IEC 60559 DFP..
> Yet, I do not see such a requirement in 5.2.4.2.3.
> 
> I do see in 6.2.5#12 that the formats are IEC 60559 DFP.
> 
> Should DEC*_EPSILON mention 'normalized'?
> 
> 
> ---
> Fred J. Tydeman        Tydeman Consulting
> tydeman at tybor.com      Testing, numerics, programming
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