[Cfp-interest 2662] Re: GB-287

[Mike Cowlishaw]

> IEEE 754 requires correctly rounded conversions between all 
> supported formats (arithmetic and non-arithmetic). Adding the 
> hexadecimal support completed the required conversions. See 
> H.4.3 and the example in H.12.2.

Just to clarify, here, a 'format' in 754, as defined in 754 clause 3, does
not include "External hexadecimal-significand character sequences" as
described in 5.12.3.   The "strings in hexadecimal format" phrase -- or
something like it -- was, I think used prior to the 2008 standard but we
were careful this century to not use the word format except for the use as
in clause 3.

5.12 does require exact conversions from binary formats to hexadecimal
strings, but not decimal:
"Implementations shall provide exact conversions from each supported binary
format to external character sequences representing numbers with hexadecimal
digits for the significand, and shall provide conversions back that recover
the original floating-point representation, except that a signaling NaN
might be converted to a quiet NaN. See 5.12.1 and 5.12.3 for details."

So I agree with Fred J. Tydeman, who wrote "there is NO requirement for
conversions between hexadecimal strings and decimal floating-point objects".

Mike