Bizarre arithmetic results

Shashwat Anand anand.shashwat at gmail.com
Thu Feb 11 13:35:26 CET 2010


Just realized my flaw

>>> .1**.1
0.79432823472428149
>>> (-.1)**(.1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: negative number cannot be raised to a fractional power

- a ** b = - (a ** b) and not (-a) ** b, Thats why -.1**.1 giving you
-0.79432823472428149 since .1 ** .1 = 0.79432823472428149 and minus sign is
appended prior to it.

On Thu, Feb 11, 2010 at 6:01 PM, Shashwat Anand <anand.shashwat at gmail.com>wrote:

> Do you really believe that -0.1 ** 0.1 is a valid computational problem ?
> Can you raise a negative number to a fractional power ?
> Output on my console (python 2.6)
>
> >>> -.1 ** .1
> -0.79432823472428149
> >>> a,b = -.1,.1
> >>> a**b
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> ValueError: negative number cannot be raised to a fractional power
> >>> -abs(a**b)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> ValueError: negative number cannot be raised to a fractional power
>
> There is a little issue here that '>>> -.1 ** .1' should give you error
> message. That is it.
>
>
>
> On Thu, Feb 11, 2010 at 6:14 AM, Terrence Cole <
> list-sink at trainedmonkeystudios.org> wrote:
>
>> Can someone explain to me what python is doing here?
>>
>> Python 3.1.1 (r311:74480, Feb  3 2010, 13:36:47)
>> [GCC 4.3.4] on linux2
>> Type "help", "copyright", "credits" or "license" for more information.
>> >>> -0.1 ** 0.1
>> -0.7943282347242815
>> >>> a = -0.1; b = 0.1
>> >>> a ** b
>> (0.7554510437117542+0.2454609236416552j)
>> >>> -abs(a ** b)
>> -0.7943282347242815
>>
>> Why does the literal version return the signed magnitude and the
>> variable version return a complex?
>>
>> Cheers,
>> Terrence
>>
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>>
>
>
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