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Re: Operator precedence problem

From Peter Pearson <pkpearson@nowhere.invalid>
Newsgroups comp.lang.python
Subject Re: Operator precedence problem
Date 2016-06-06 16:58 +0000
Message-ID <drlodcFejipU1@mid.individual.net> (permalink)
References <816c651a-d0ae-4e23-a5b2-72a8f7398468@googlegroups.com> <CAPTjJmoQKmhAWU0m9+xkd7SGG=UCVVuuxrdgDwG-wDeVNCLqpQ@mail.gmail.com> <mailman.10.1465143880.2306.python-list@python.org>

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On Mon, 6 Jun 2016 02:24:37 +1000, Chris Angelico <rosuav@gmail.com> wrote:
> On Sun, Jun 5, 2016 at 4:53 PM, ICT Ezy <ictezy@gmail.com> wrote:
>>>>> 2 ** 3 ** 2
>> Answer is 512
>> Why not 64?
>> Order is right-left or left-right?
>
> This example follows the mathematical standard; you start from the
> "top" (the right hand side), and work your way down.
[snip]

This is almost certainly why top-down was the desirable choice.  And
as for why mathematicians chose top-down (probably long before any
programming-language designer faced the decision), note that this
convention allows you to write both (a**b)**c and a**(b**c) without
parentheses, making expressions cleaner than otherwise:

               bc
  (a**b)**c = a

                c
               b
  a**(b**c) = a

-- 
To email me, substitute nowhere->runbox, invalid->com.

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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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