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Re: Operator precedence problem

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From Uri Even-Chen <uri@speedy.net>
Newsgroups comp.lang.python
Subject Re: Operator precedence problem
Date Sun, 5 Jun 2016 19:05:16 +0300
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My suggestion: Never write expressions, such as  2 ** 3 ** 2 or even 2 * 4
+ 5, without parentheses. Always add parentheses - 2 ** (3 ** 2) (or (2 **
3) **2) or (2 * 4) + 5 (or 2 * (4 + 5)).


*Uri Even-Chen*
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On Sun, Jun 5, 2016 at 6:05 PM, ICT Ezy <ictezy@gmail.com> wrote:

> On Sunday, June 5, 2016 at 1:06:21 PM UTC+5:30, Peter Otten wrote:
> > ICT Ezy wrote:
> >
> > >>>> 2 ** 3 ** 2
> > > Answer is 512
> > > Why not 64?
> > > Order is right-left or left-right?
> >
> > ** is a special case:
> >
> > """
> > The power operator ** binds less tightly than an arithmetic or bitwise
> unary
> > operator on its right, that is, 2**-1 is 0.5.
> > """
> > https://docs.python.org/3.5/reference/expressions.html#id21
> >
> > Here's a little demo:
> >
> > $ cat arithdemo.py
> > class A:
> >     def __init__(self, value):
> >         self.value = str(value)
> >     def __add__(self, other):
> >         return self._op(other, "+")
> >     def __pow__(self, other):
> >         return self._op(other, "**")
> >     def __repr__(self):
> >         return self.value
> >     def _op(self, other, op):
> >         return A("({} {} {})".format(self.value, op, other.value))
> > $ python3 -i arithdemo.py
> > >>> A(1) + A(2) + A(3)
> > ((1 + 2) + 3)
> > >>> A(1) ** A(2) ** A(3)
> > (1 ** (2 ** 3))
>
> Thank you very much for your explanation
> --
> https://mail.python.org/mailman/listinfo/python-list
>

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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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