[Python-Dev] [Python-checkins] r64424 - in python/trunk:Include/object.h Lib/test/test_sys.py Misc/NEWSObjects/intobject.c Objects/longobject.c Objects/typeobject.cPython/bltinmodule.c

[Guido van Rossum]

On Fri, Jun 27, 2008 at 2:54 PM, Mark Dickinson <dickinsm at gmail.com> wrote:
> On Fri, Jun 27, 2008 at 8:02 PM, Guido van Rossum <guido at python.org> wrote:
>> Now that I've learned about the hex float format supported by C++ and
>> Java, I wonder if it wouldn't be better to support conversion to and
>> from that format and nothing else.
>>
>> E.g.
>>
>>>>> math.tohex(3.14)
>> '0x1.91eb851eb851fp+1'
>>>>> math.fromhex('0x1.91eb851eb851fp+1')
>> 3.1400000000000001
>
> This would certainly be enough for me, though I think there's still
> some educational value in having binary output available.  But
> that's just a matter of substituting a four-bit binary string for
> each hexadecimal digit (or learning to read hexadecimal as
> though it were binary).

If it's educational it can be left as an exercise for the reader. :-)

> In fromhex, what would be done with a string that gives more
> hex digits than the machine precision can support?  An obvious
> answer is just to round to the nearest float, but since part of the
> point of hex floats is having a way to specify a given value
> *exactly*, it might make more sense to raise an exception
> rather than changing the value by rounding it.

Whatever Java and C99 do.

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)