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From: Jussi Piitulainen on 11 Feb 2010 11:23
Robert Kern writes:
> On 2010-02-11 06:31 AM, Shashwat Anand wrote:
> > There is a little issue here that '>>> -.1 ** .1' should give you
> > error message. That is it.
>
> No, fractional powers of negative numbers are perfectly valid
> mathematically. The result is a complex number. In Python 3 (what
> the OP is using), this has been implemented, but not in Python 2.6.

Perhaps it should raise a MisleadingSpacingError at compile time. The
error message could recommend - .1**.1, or better -(.1 ** .1).
From: Terry Reedy on 11 Feb 2010 17:52
On 2/11/2010 11:23 AM, Jussi Piitulainen wrote:
> Robert Kern writes:
>> On 2010-02-11 06:31 AM, Shashwat Anand wrote:
>>> There is a little issue here that '>>> -.1 ** .1' should give you
>>> error message. That is it.
>>
>> No, fractional powers of negative numbers are perfectly valid
>> mathematically. The result is a complex number. In Python 3 (what
>> the OP is using), this has been implemented, but not in Python 2.6.
>
> Perhaps it should raise a MisleadingSpacingError at compile time.

You forgot the smiley ;-).

> The error message could recommend - .1**.1, or better -(.1 ** .1).

The compiler would never see the difference between -.1 ** .1 and the
first and probably no difference with the second either.


From: Aahz on 11 Feb 2010 21:44
In article <hl1j4a$j61$2(a)reader2.panix.com>,
Grant Edwards <invalid(a)invalid.invalid> wrote:
>
>Didn't we just do this one last week?

Let's do the Time Warp again!
--
Aahz (aahz(a)pythoncraft.com) <*> http://www.pythoncraft.com/

"At Resolver we've found it useful to short-circuit any doubt and just
refer to comments in code as 'lies'. :-)"
From: Jussi Piitulainen on 12 Feb 2010 04:40
Terry Reedy writes:
> On 2/11/2010 11:23 AM, Jussi Piitulainen wrote:
> > Robert Kern writes:
> >> On 2010-02-11 06:31 AM, Shashwat Anand wrote:
> >>> There is a little issue here that '>>> -.1 ** .1' should give you
> >>> error message. That is it.
> >>
> >> No, fractional powers of negative numbers are perfectly valid
> >> mathematically. The result is a complex number. In Python 3 (what
> >> the OP is using), this has been implemented, but not in Python 2.6.
> >
> > Perhaps it should raise a MisleadingSpacingError at compile time.
>
> You forgot the smiley ;-).
>
> > The error message could recommend - .1**.1, or better -(.1 ** .1).
>
> The compiler would never see the difference between -.1 ** .1 and the
> first and probably no difference with the second either.

It could be done the same way that the compiler keeps track of the
source line numbers now: early phases annotate their output with any
information that later phases may need. This error would be detected
during syntactic analysis.

:)
From: Terry Reedy on 12 Feb 2010 11:08
On 2/12/2010 4:40 AM, Jussi Piitulainen wrote:
> Terry Reedy writes:
>> On 2/11/2010 11:23 AM, Jussi Piitulainen wrote:
>>> Robert Kern writes:
>>>> On 2010-02-11 06:31 AM, Shashwat Anand wrote:
>>>>> There is a little issue here that '>>> -.1 ** .1' should give you
>>>>> error message. That is it.
>>>>
>>>> No, fractional powers of negative numbers are perfectly valid
>>>> mathematically. The result is a complex number. In Python 3 (what
>>>> the OP is using), this has been implemented, but not in Python 2.6.
>>>
>>> Perhaps it should raise a MisleadingSpacingError at compile time.
>>
>> You forgot the smiley ;-).
>>
>> > The error message could recommend - .1**.1, or better -(.1 ** .1).
>>
>> The compiler would never see the difference between -.1 ** .1 and the
>> first and probably no difference with the second either.
>
> It could be done the same way that the compiler keeps track of the
> source line numbers now: early phases annotate their output with any
> information that later phases may need. This error would be detected
> during syntactic analysis.

There is no error to detect. Sorry, read the manual and either learn or
lookup precedence rules (there is a table in the end of the Expressions
chapter) or use parentheses when not sure.


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