[Cfp-interest 2485] Re: 5.2.4.2.3 and IEC 60559

[Vincent Lefevre]

On 2022-08-01 22:46:01 -0500, Fred J. Tydeman 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.

I think that should also be put in 5.2.4.2.3.

BTW, does the standard clearly say that these types are optional?
This just seems to be suggested by 5.2.4.2.3, but 6.2.5#12 says
no more than "There are three decimal floating types, designated
as _Decimal32, _Decimal64, and _Decimal128. Respectively, they
have the IEC 60559 formats: decimal32, decimal64, and decimal128.
Decimal floating types are real floating types.", which could be
interpreted as such types being mandatory. Compare with _Complex,
for which it is said "Complex types are a conditional feature that
implementations need not support;".

Moreover, it seems that if one of these 3 types is supported, then
the 3 of them need to be supported. Is this wanted?

> Should DEC*_EPSILON mention 'normalized'?

This is useless for a true FP format, like the IEC 60559 formats, due
to the "greater than 1". The "normalized" for the float, double and
long double types was necessary because additional values are allowed,
which in the case of the double-double format for long double (where
the math value 1 + DBL_MIN is representable in long double).

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