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Re: [PATCH] Remove GMP in favor of MPFR
I wrote:
>>>
>>> I'm looking at the July 1, 2004 revision of the IEEE-754 standard.
>>> Table 1a shows
>>> p emax emin
>>> binary32 24 127 -126
>>> binary64 53 1023 -1022
>>> binary128 113 16383 -16382
>>>
Paul wrote:
>>
>>I think these numbers come from gcc/real.c. However reading a bit further
>>uncovers the following comment:
>> /* Recall that IEEE numbers are interpreted as 1.F x 2**exp,
>> whereas the intermediate representation is 0.F x 2**exp.
>
> That should be 0.5F x 2**exp
There isn't a "5" in the set of digits when writing the
significand in a binary representation.
> Yes, IEEE and Fortran differ by 1 in the definition of exponent. C
> <float.h> agrees with Fortran. Source code which uses the C and Fortran
> facilities must not have to be concerned with the different IEEE
> definition. You can't even tell from the raw number format. To IEEE, the
> bias is different by 1 from the bias which goes with the Fortran/C
> definition.
Are you suggesting that we should use p, emin, and emax that are
consistent with float.h?
--
Steve