[Cfp-interest 2497] Re: 5.2.4.2.3 and IEC 60559

[Mike Cowlishaw]

> 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?

I thought all floating-points types are optional, since they don't have to
be implemented on machines that don't have FP hardware?

> 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.

The 'real' here is meant to be a reference to them being approximations to
the real numbers, I suspect.

> Compare with _Complex, for which it is said "Complex types are a 
> conditional feature that implementations need not support;".

Which also would seem to be superfluous.  I think pointing this out all over
the place is just noise.  And also, I think at some point one has to draw a
line and call this one 'done'.  Time to start a wish/errata list, perhaps,
for the next revision.

Mike