Why does python break IEEE 754 for 1.0/0.0 and 0.0/0.0?

[Grant Edwards]

On 2005-07-14, Martin v. Löwis <martin at v.loewis.de> wrote:

>> 1/0 is defined by the standard as +Inf and 0/0 is NaN.
>
> I wonder why Tim hasn't protested here: I thought this was *not*
> the case. I thought IEEE 754 defined +Inf and NaN as only a possible
> outcome of these operations with other possible outcomes being
> exceptions...

The "exceptions" specified by the standard aren't required, but
it's "strongly recommended" that they be provided as options
for the programmer.  If provided, I believe they are to be
resumable so that the user can determine what operation was
attempted on what operands and return a result if desired.

> In that case, Python would comply to IEEE 754 in this respect

My recollection is that returning Inf and NaN is to be the
default behavior, and a resumable exception is a recommended
option.

> (although in a different way than the C implementation on the
> same system).

I can't find my copy of the standard at the moment, though I
did just re-read Goldberg's 1991 discussion of the standard.

-- 
Grant Edwards                   grante             Yow!  My Aunt MAUREEN was
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