On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
> Grant Edwards wrote:
>> On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
>>>Several issues:
>>
>>
>>>(1) The number of distinct NaNs varies among platforms.
>>
>> According to the IEEE standard, there are exactly two:
>> signalling and quiet, and on platforms that don't impliment
>> floating point exceptions (probably in excess of 99.9% of
>> python installations), the difference between the two is moot.
>
> But it does not specify the representation of such NaNs.
Yes, it does. It specifies it exactly: certain bits are ones,
certain other bits are zeros. I don't know how much more exactly
the representation can be defined.
>> The bit patterns are defined by the IEEE 754 standard.
> Perhaps this is right and I misunderstand the standard, but my
> understanding is that the full bit pattern is not, in fact,
> defined.
The represntation of NaNs, infinities, normalized numbers and
denormal numbers are all completely defined by the standard.
>> If there are Python-hosting platoforms that don't use IEEE 754 as
>> the floating point representation, then that can be dealt with.
> There are.
That's where it gets nasty.
>> Python has _tons_ of platform-specific code in it.
> But the _tons_ are written in C89 C.
True.
> It is not taboo. I am trying to explain why it is not a
> trivial task, but a substantial effort.
It's trivial for platforms that obey the IEEE 754 standard.
> If you are willing to perform the substantial effort, good on
> you, and I'll help. If you simply want to implement on the two
> platforms you use, and want everyone else to implement the
> interface you choose, that seems to me an unreasonable
> request.
I would think that implimenenting things according to the IEEE
standard and letting non-standard platforms figure out what to
do for themselves would seem a reasonable approach.
--
Grant Edwards grante Yow! Now I understand the
at meaning of "THE MOD SQUAD"!
visi.com
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