Re: Operator precedence problem

From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Subject	Re: Operator precedence problem
Date	2016-06-07 02:21 +1000
Message-ID	<mailman.41.1465230098.2306.python-list@python.org> (permalink)
References	(12 earlier) <slrnnlb5jj.6f8.jon+usenet@sable.unequivocal.co.uk> <CAPTjJmq7vkfZmNndbJn-azX+c8KwjW3uZCzprYdcYU+aM8Ec9A@mail.gmail.com> <mailman.40.1465228656.2306.python-list@python.org> <slrnnlb7pl.6f8.jon+usenet@sable.unequivocal.co.uk> <CAPTjJmrEiUS0KrnpFdwUyd2vtqnd0aAruztxVgG_6zZdMe4a=A@mail.gmail.com>

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On Tue, Jun 7, 2016 at 2:05 AM, Jon Ribbens
<jon+usenet@unequivocal.co.uk> wrote:
> On 2016-06-06, Chris Angelico <rosuav@gmail.com> wrote:
>> On Tue, Jun 7, 2016 at 1:27 AM, Jon Ribbens
>><jon+usenet@unequivocal.co.uk> wrote:
>>>>> You should put brackets around expressions when it's at all unclear
>>>>> what the meaning is. You could think of them a bit like "active
>>>>> comments" I suppose.
>>>>
>>>> Your code should keep noise to the minimum.
>>>
>>> Sensible and beneficial comments aren't "noise".
>>
>> In that case, please never insult the intelligence of your future
>> readers by including any of these parentheses:
>>
>> x = 1 + (2 * 3)
>
> I'm not sure what your point is. Yes, obviously you can take anything
> to ridiculous extremes - that's why I said "sensible".

Earlier in this thread, it was suggested that parens always be used,
even for this kind of example.

>> value = 77 if (x % 2) else (70*7)
>
> I'm not convinced that one isn't actually a good idea. It does seem
> to aid the readability (especially if you space '70 * 7' properly).
> If the expressions were any more complex then it would be even more
> likely to be a good idea.

Hmm, I still think not. But if you want the parens, at least
acknowledge that they're not to enforce/remind of operator precedence.

>> And if your readers have to figure out what 3**3**3 is interpreted as,
>> there should be an interactive interpreter around. Or here - try
>> something cute:
>>
>>>>> 2**2**-1
>
> I can't tell now if you're agreeing with me or disagreeing, because
> you started out sounding like you were disagreeing but then provided
> an example that helps prove my point.

My point is that if you're not sure, you grab interactive Python and
give it a quick whirl. Usually easier AND quicker than the
alternatives.

ChrisA

Thread

Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-04 23:53 -0700
  Re: Operator precedence problem Peter Otten <__peter__@web.de> - 2016-06-05 09:35 +0200
    Re: Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-05 08:05 -0700
      Re: Operator precedence problem Uri Even-Chen <uri@speedy.net> - 2016-06-05 19:05 +0300
        Re: Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-05 20:24 -0700
        Re: Operator precedence problem Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-05 22:46 -0700
          Re: Operator precedence problem Random832 <random832@fastmail.com> - 2016-06-06 09:57 -0400
            Re: Operator precedence problem Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 17:22 +0300
              Re: Operator precedence problem Random832 <random832@fastmail.com> - 2016-06-06 10:35 -0400
                Re: Operator precedence problem Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 17:55 +0300
              Re: Operator precedence problem Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2016-06-06 15:03 +0000
                Re: Operator precedence problem Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 18:22 +0300
                Re: Operator precedence problem Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2016-06-06 15:27 +0000
                Re: Operator precedence problem Chris Angelico <rosuav@gmail.com> - 2016-06-07 01:57 +1000
                Re: Operator precedence problem Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2016-06-06 16:05 +0000
                Re: Operator precedence problem Chris Angelico <rosuav@gmail.com> - 2016-06-07 02:21 +1000
                Re: Operator precedence problem Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2016-06-06 17:02 +0000
                Re: Operator precedence problem Grant Edwards <grant.b.edwards@gmail.com> - 2016-06-06 16:51 +0000
              Re: Operator precedence problem Peter Otten <__peter__@web.de> - 2016-06-06 18:38 +0200
            Re: Operator precedence problem Steven D'Aprano <steve@pearwood.info> - 2016-06-07 03:07 +1000
              Re: Operator precedence problem Random832 <random832@fastmail.com> - 2016-06-06 14:44 -0400
                Re: Operator precedence problem Marko Rauhamaa <marko@pacujo.net> - 2016-06-06 21:49 +0300
              Re: Operator precedence problem MRAB <python@mrabarnett.plus.com> - 2016-06-06 20:17 +0100
                Re: Operator precedence problem Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-07 11:27 +1200
            Re: Operator precedence problem Rustom Mody <rustompmody@gmail.com> - 2016-06-06 10:14 -0700
              Re: Operator precedence problem Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-06 21:09 +0100
      Re: Operator precedence problem Michael Torrie <torriem@gmail.com> - 2016-06-05 17:47 -0600
        Re: Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-05 20:23 -0700
  Re: Operator precedence problem Chris Angelico <rosuav@gmail.com> - 2016-06-06 02:24 +1000
    Re: Operator precedence problem Peter Pearson <pkpearson@nowhere.invalid> - 2016-06-06 16:58 +0000
      Re: Operator precedence problem Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-07 11:21 +1200
  Re: Operator precedence problem Random832 <random832@fastmail.com> - 2016-06-05 13:19 -0400
    Re: Operator precedence problem ICT Ezy <ictezy@gmail.com> - 2016-06-05 20:23 -0700
  Re: Operator precedence problem Gary Herron <gherron@digipen.edu> - 2016-06-05 00:04 -0700

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