Re: Coolest Python recipe of all time

From	Terry Reedy <tjreedy@udel.edu>
Subject	Re: Coolest Python recipe of all time
Date	2011-05-03 02:00 -0400
References	<69c1813d-1a9a-4686-9768-8ec1910a45f8@d19g2000prh.googlegroups.com> <ak5ur6pugqvjrs4dthlpp5j4q1i6h0gimv@4ax.com> <mailman.1079.1304369965.9059.python-list@python.org> <018ur6da31iv7us9gm4dpgl7tfl0i6snb2@4ax.com> <ipo2df$14c$1@dough.gmane.org>
Newsgroups	comp.lang.python
Message-ID	<mailman.1098.1304402417.9059.python-list@python.org> (permalink)

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On 5/3/2011 1:04 AM, Stefan Behnel wrote:

> The bad thing about this recipe is that it requires quite a bit of
> background knowledge in order to infer that the code the developer is
> looking at is actually correct.

The main math knowledge needed is the trivial fact that if a*x + b = 0, 
then x = -b/a. The other math knowledge needed is that complex numbers 
add componentwise. The trick is that replacing x with j and evaluating 
therefore causes (in Python) all the coefficients of x (now j) to be 
added together separately from all the constant terms to reduce the 
linear equation to a*x+b (= 0 implied).

-- 
Terry Jan Reedy

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Coolest Python recipe of all time Raymond Hettinger <python@rcn.com> - 2011-05-02 10:33 -0700
  Re: Coolest Python recipe of all time David Monaghan <monaghand.david@gmail.com> - 2011-05-02 21:48 +0100
    Re: Coolest Python recipe of all time Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-02 14:58 -0600
      Re: Coolest Python recipe of all time David Monaghan <monaghand.david@gmail.com> - 2011-05-02 22:45 +0100
        Re: Coolest Python recipe of all time Stefan Behnel <stefan_ml@behnel.de> - 2011-05-03 07:04 +0200
          Re: Coolest Python recipe of all time Raymond Hettinger <python@rcn.com> - 2011-05-03 09:43 -0700
            Re: Coolest Python recipe of all time Chris Angelico <rosuav@gmail.com> - 2011-05-04 07:54 +1000
            Re: Coolest Python recipe of all time Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-03 16:10 -0600
        Re: Coolest Python recipe of all time Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-02 23:17 -0600
        Re: Coolest Python recipe of all time Terry Reedy <tjreedy@udel.edu> - 2011-05-03 02:00 -0400
          Re: Coolest Python recipe of all time Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-05-03 18:29 +1200
            Re: Coolest Python recipe of all time Terry Reedy <tjreedy@udel.edu> - 2011-05-03 11:49 -0400
            Re: Coolest Python recipe of all time Raymond Hettinger <python@rcn.com> - 2011-05-03 09:32 -0700
            Re: Coolest Python recipe of all time geremy condra <debatem1@gmail.com> - 2011-05-03 09:51 -0700
        Re: Coolest Python recipe of all time Stefan Behnel <stefan_ml@behnel.de> - 2011-05-03 08:23 +0200
          Re: Coolest Python recipe of all time Raymond Hettinger <python@rcn.com> - 2011-05-03 15:19 -0700
  Re: Coolest Python recipe of all time Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-06 16:59 +0000
    Re: Coolest Python recipe of all time geremy condra <debatem1@gmail.com> - 2011-05-06 10:43 -0700
    Re: Coolest Python recipe of all time Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-06 12:36 -0600
      Re: Coolest Python recipe of all time Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-07 08:29 +0000
        Re: Coolest Python recipe of all time Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-07 08:54 -0600
        Re: Coolest Python recipe of all time Raymond Hettinger <python@rcn.com> - 2011-05-07 14:02 -0700
    Re: Coolest Python recipe of all time Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-06 13:38 -0600
    Re: Coolest Python recipe of all time Raymond Hettinger <python@rcn.com> - 2011-05-06 12:58 -0700
  RE: Coolest Python recipe of all time Trent Nelson <trent@snakebite.org> - 2011-05-09 02:31 -0700

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