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Re: Coolest Python recipe of all time

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From Ian Kelly <ian.g.kelly@gmail.com>
Date Fri, 6 May 2011 13:38:08 -0600
Subject Re: Coolest Python recipe of all time
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On Fri, May 6, 2011 at 12:36 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> This is typically implemented using continuations, and I'm not sure
> whether a true amb could actually be achieved in Python without adding
> continuations or flow-control macros to the language.

I stand corrected.  After poking around a bit more I found this recipe
that is designed for unit-testing but implements amb beautifully.

http://lackingrhoticity.blogspot.com/2009/08/how-to-do-model-checking-of-python-code.html

My code from the previous post using this recipe:

def find_values(chooser):
    def amb(*choices):
        return chooser.choose(choices)
    def require(x):
        if not x:
            amb()
    a = amb(1, 3, 5)
    b = amb(2, 4, 8)
    require(a + b > 5)
    require(is_prime(a * b + 1))
    c = amb(a, b, None)
    require(c is None or c >= 5)
    return a, b, c

check(find_values)

The one downside is that the check function (again, designed for
unit-testing) does not provide any way to retrieve the returned
values, but that is easily solved by rewriting as a generator.

Cheers,
Ian

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Thread

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
    Re: Coolest Python recipe of all time Raymond Hettinger <python@rcn.com> - 2011-05-09 14:10 -0700

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