Re: Encapsulation unpythonic?

From	Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject	Re: Encapsulation unpythonic?
Date	2013-09-03 22:41 -0400
Organization	IISS Elusive Unicorn
References	(1 earlier) <8c7c4854-70e1-46e7-a3ff-a3206c4c5c27@googlegroups.com> <5221567b$0$6599$c3e8da3$5496439d@news.astraweb.com> <ecd32f98-6ba8-4b1e-91d3-e0fd6a8034c3@googlegroups.com> <5221d7ab$0$6599$c3e8da3$5496439d@news.astraweb.com> <op.w2s4vswqa8ncjz@gnudebeest>
Newsgroups	comp.lang.python
Message-ID	<mailman.22.1378262483.5461.python-list@python.org> (permalink)

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On Tue, 03 Sep 2013 00:29:42 +0100, "Rhodri James"
<rhodri@wildebst.demon.co.uk> declaimed the following:

>On Sat, 31 Aug 2013 12:46:52 +0100, Steven D'Aprano  
><steve+comp.lang.python@pearwood.info> wrote:
>
>> # THIS DOES NOT HAPPEN IN PYTHON
>> # or any other language, as far as I am aware
>> x = 23
>> y = x  # y now has the value 23
>> x = 42  # change the value of the object  ### NOT SO! ###
>> print y
>> => prints 42
>
>Not directly, but FORTRAN did (does?) allow you to achieve this  
>oh-so-undesirable result indirectly.
>
>FORTRAN passes arguments to functions and procedures by reference.  That  
>includes passing constants, which effectively get put into hidden  
>variables and passed across.  Changes to the "constant" parameters in the  
>function can happen just as with any pass-by-reference, which would be  
>fine if you promptly threw the constant away.  Unfortunately smart  
>compilers used to (still do?) keep pools of these common constant  
>"variables" around rather than creating new ones all the time, so changes  
>to "constants" persisted.  Many's the poor natural scientist who was  
>perplexed to find that 0 suddenly had the value 1!

	Granted, this tended to be with older implementations. Most more modern
(F77 and later) tend to allocate such literals in a read-only block of
memory, so attempts to change them now cause a significant program failure.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

Thread

Encapsulation unpythonic? fsaldan1@gmail.com - 2013-08-17 05:26 -0700
  Re: Encapsulation unpythonic? Skip Montanaro <skip@pobox.com> - 2013-08-17 07:54 -0500
  Re: Encapsulation unpythonic? David <bouncingcats@gmail.com> - 2013-08-17 23:05 +1000
  Re: Encapsulation unpythonic? Chris Angelico <rosuav@gmail.com> - 2013-08-17 16:50 +0100
  Re: Encapsulation unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-08-17 16:17 +0000
    Re: Encapsulation unpythonic? Joshua Landau <joshua@landau.ws> - 2013-08-18 18:15 +0100
      Re: Encapsulation unpythonic? Steven D'Aprano <steve@pearwood.info> - 2013-08-19 07:05 +0000
        Re: Encapsulation unpythonic? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-08-19 18:57 -0400
        Re: Encapsulation unpythonic? random832@fastmail.us - 2013-08-21 12:52 -0400
          Re: Encapsulation unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-08-22 02:06 +0000
        Re: Encapsulation unpythonic? Ian Kelly <ian.g.kelly@gmail.com> - 2013-08-21 16:02 -0600
  Re: Encapsulation unpythonic? Gary Herron <gary.herron@islandtraining.com> - 2013-08-17 13:16 -0700
  Re: Encapsulation unpythonic? Terry Reedy <tjreedy@udel.edu> - 2013-08-17 17:22 -0400
  Re: Encapsulation unpythonic? Chris Angelico <rosuav@gmail.com> - 2013-08-18 01:59 +0100
  Re: Encapsulation unpythonic? chaz2cry@gmail.com - 2013-08-22 19:12 -0700
  Re: Encapsulation unpythonic? Fabrice Pombet <fp2161@gmail.com> - 2013-08-30 10:43 -0700
    Re: Encapsulation unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-08-31 02:35 +0000
      Re: Encapsulation unpythonic? Fabrice Pombet <fp2161@gmail.com> - 2013-08-30 23:07 -0700
        Re: Encapsulation unpythonic? Marco Buttu <marco.buttu@gmail.com> - 2013-08-31 08:49 +0200
        Re: Encapsulation unpythonic? Gary Herron <gherron@digipen.edu> - 2013-08-31 00:03 -0700
          Re: Encapsulation unpythonic? Fabrice Pombet <fp2161@gmail.com> - 2013-08-31 00:42 -0700
            Re: Encapsulation unpythonic? Fabrice Pombet <fp2161@gmail.com> - 2013-08-31 01:00 -0700
        Re: Encapsulation unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-08-31 11:46 +0000
          Re: Encapsulation unpythonic? Ned Batchelder <ned@nedbatchelder.com> - 2013-08-31 08:41 -0400
            Re: Encapsulation unpythonic? Fabrice Pombet <fp2161@gmail.com> - 2013-08-31 05:49 -0700
          Re: Encapsulation unpythonic? Fabrice Pombet <fp2161@gmail.com> - 2013-08-31 05:57 -0700
            Re: Encapsulation unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-01 08:10 +0000
              Re: Encapsulation unpythonic? Chris Angelico <rosuav@gmail.com> - 2013-09-01 18:21 +1000
                Re: Encapsulation unpythonic? Fabrice Pombet <fp2161@gmail.com> - 2013-09-01 03:09 -0700
                Re: Encapsulation unpythonic? Ethan Furman <ethan@stoneleaf.us> - 2013-09-01 11:42 -0700
                Re: Encapsulation unpythonic? Roy Smith <roy@panix.com> - 2013-09-01 15:13 -0400
                Re: Encapsulation unpythonic? Ethan Furman <ethan@stoneleaf.us> - 2013-09-01 13:33 -0700
                Re: Encapsulation unpythonic? Tim Delaney <timothy.c.delaney@gmail.com> - 2013-09-02 07:54 +1000
                Re: Encapsulation unpythonic? Roy Smith <roy@panix.com> - 2013-09-01 18:02 -0400
                Re: Encapsulation unpythonic? Ethan Furman <ethan@stoneleaf.us> - 2013-09-01 17:24 -0700
                Re: Encapsulation unpythonic? Roy Smith <roy@panix.com> - 2013-09-01 20:59 -0400
                Re: Encapsulation unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-02 02:57 +0000
                Re: Encapsulation unpythonic? Ethan Furman <ethan@stoneleaf.us> - 2013-09-01 21:15 -0700
                Re: Encapsulation unpythonic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-02 01:57 +0000
              Re: Encapsulation unpythonic? Ben Finney <ben+python@benfinney.id.au> - 2013-09-02 09:32 +1000
                Re: Encapsulation unpythonic? Roy Smith <roy@panix.com> - 2013-09-01 20:52 -0400
          Re: Encapsulation unpythonic? "Rhodri James" <rhodri@wildebst.demon.co.uk> - 2013-09-03 00:29 +0100
            Re: Encapsulation unpythonic? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-09-03 22:41 -0400
        Re: Encapsulation unpythonic? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-08-31 13:31 -0400
        Re: Encapsulation unpythonic? Tim Delaney <timothy.c.delaney@gmail.com> - 2013-09-01 03:47 +1000
    Re: Encapsulation unpythonic? 88888 Dihedral <dihedral88888@gmail.com> - 2013-09-02 14:43 -0700

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