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Re: Language design

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Date Fri, 13 Sep 2013 07:53:39 +1000
Subject Re: Language design
From Chris Angelico <rosuav@gmail.com>
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On Fri, Sep 13, 2013 at 4:13 AM, Markus Rother <python@markusrother.de> wrote:
> On 12.09.2013 01:27, Chris Angelico wrote:
>> On Thu, Sep 12, 2013 at 6:41 AM, Markus Rother <python@markusrother.de> wrote:
>>>     3. The default return value of methods is None instead of self.
>>>     If it was self, it would be possible to chain method calls (which
>>>     is called a cascade in smalltalk).
>>
>> That's a policy decision: a method (or function) will *EITHER* return
>> a value, *OR* mutate its primary argument (in the case of a method,
>> that's self).
>
> You are stating: "All getters must be free of side effects".
> That is not the case.  Furthermore, the demand for getters with hidden
> side effects is the reasoning behind properties.

This isn't a language feature here, just a stdlib policy. It's more
akin to Ruby's habit of adorning the mutating methods with an
exclamation mark - it's a way of stopping you from accidentally doing
what you didn't mean to do. There's a sharp distinction between
list.sort(), which mutates in place and returns None, and sorted(),
which doesn't touch its argument and returns a new list.

ChrisA

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Thread

Language design Steven D'Aprano <steve@pearwood.info> - 2013-09-10 06:09 +0000
  Re: Language design diverman <pavel@schon.cz> - 2013-09-09 23:59 -0700
  Re: Language design Ben Finney <ben+python@benfinney.id.au> - 2013-09-10 17:07 +1000
    Re: Language design Nobody <nobody@nowhere.com> - 2013-09-11 01:03 +0100
      Re: Language design Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-11 00:53 +0000
        Re: Language design Nobody <nobody@nowhere.com> - 2013-09-12 18:23 +0100
  Re: Language design Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-09-10 09:58 +0200
  Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-10 20:20 +1000
  Re: Language design Chris Rebert <clp2@rebertia.com> - 2013-09-10 18:46 -0700
  Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-11 14:21 +1000
  Re: Language design Burak Arslan <burak.arslan@arskom.com.tr> - 2013-09-11 13:38 +0300
    Re: Language design Neil Cerutti <neilc@norwich.edu> - 2013-09-11 14:32 +0000
      Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-12 00:46 +1000
  Re: Language design Wayne Werner <wayne@waynewerner.com> - 2013-09-11 06:42 -0500
  Re: Language design Dave Angel <davea@davea.name> - 2013-09-11 12:05 +0000
  Re: Language design Ethan Furman <ethan@stoneleaf.us> - 2013-09-11 07:52 -0700
  Re: Language design Burak Arslan <burak.arslan@arskom.com.tr> - 2013-09-11 18:41 +0300
  Re: Language design Markus Rother <python@markusrother.de> - 2013-09-11 22:41 +0200
    Re: Language design Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-11 23:40 +0000
  Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-11 14:22 -0700
  Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-11 14:30 -0700
    Re: Language design Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-11 23:40 +0000
      Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-11 17:49 -0700
        Re: Language design Steven D'Aprano <steve@pearwood.info> - 2013-09-12 05:33 +0000
          Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-12 20:23 -0700
            Re: Language design Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-13 05:08 +0000
              Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-13 17:39 +1000
              Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-14 19:37 -0700
              Re: Language design Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-09-15 09:57 +0200
      Re: Language design Terry Reedy <tjreedy@udel.edu> - 2013-09-11 21:40 -0400
      Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-12 11:41 +1000
  Re: Language design Ethan Furman <ethan@stoneleaf.us> - 2013-09-11 14:15 -0700
  RE: Language design "Prasad, Ramit" <ramit.prasad@jpmorgan.com.dmarc.invalid> - 2013-09-11 21:56 +0000
  Re: Language design Ben Finney <ben+python@benfinney.id.au> - 2013-09-12 09:16 +1000
  Please omit false legalese footers (was: Language design) Ben Finney <ben+python@benfinney.id.au> - 2013-09-12 09:22 +1000
    Re: Please omit false legalese footers (was: Language design) Grant Edwards <invalid@invalid.invalid> - 2013-09-12 20:12 +0000
  Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-12 09:27 +1000
  Re: Language design Ben Finney <ben+python@benfinney.id.au> - 2013-09-12 09:19 +1000
  Re: Language design Terry Reedy <tjreedy@udel.edu> - 2013-09-11 19:51 -0400
  Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-11 17:25 -0700
  Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-12 10:31 +1000
    Re: Language design Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-12 02:33 +0000
      Re: Language design Roy Smith <roy@panix.com> - 2013-09-11 22:43 -0400
        Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-12 12:58 +1000
        Re: Language design Steven D'Aprano <steve@pearwood.info> - 2013-09-12 05:08 +0000
  Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-11 17:34 -0700
  Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-11 17:37 -0700
  Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-12 10:40 +1000
  Re: Language design Benjamin Kaplan <benjamin.kaplan@case.edu> - 2013-09-11 17:54 -0700
  Re: Language design Ben Finney <ben+python@benfinney.id.au> - 2013-09-12 10:57 +1000
  Re: Language design Joshua Landau <joshua@landau.ws> - 2013-09-12 05:17 +0100
  Re: Please omit false legalese footers (was: Language design) Skip Montanaro <skip@pobox.com> - 2013-09-12 04:27 -0500
  Re: Please omit false legalese footers (was: Language design) Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-09-12 10:44 +0100
  Re: Language design Markus Rother <python@markusrother.de> - 2013-09-12 19:51 +0200
    Re: Language design Neil Cerutti <neilc@norwich.edu> - 2013-09-12 18:06 +0000
  Re: Language design Markus Rother <python@markusrother.de> - 2013-09-12 20:13 +0200
  Re: Language design Markus Rother <python@markusrother.de> - 2013-09-12 20:24 +0200
    Re: Language design Neil Cerutti <neilc@norwich.edu> - 2013-09-12 19:18 +0000
  Re: Language design Ethan Furman <ethan@stoneleaf.us> - 2013-09-12 11:05 -0700
  Re: Language design Ned Batchelder <ned@nedbatchelder.com> - 2013-09-12 14:37 -0400
  Re: Language design Terry Reedy <tjreedy@udel.edu> - 2013-09-12 14:46 -0400
  Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-13 07:53 +1000
  Re: Language design Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-09-13 09:04 +0200
    Re: Language design Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-13 10:13 +0000
      Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-13 21:16 +1000
      Re: Language design Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-09-13 13:28 +0200
      Re: Language design Terry Reedy <tjreedy@udel.edu> - 2013-09-13 15:32 -0400
      Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-14 09:57 +1000
        Re: Language design Neil Cerutti <neilc@norwich.edu> - 2013-09-18 14:57 +0000
          Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-19 01:02 +1000
            Re: Language design Neil Cerutti <neilc@norwich.edu> - 2013-09-18 15:08 +0000
              Re: Language design Chris Angelico <rosuav@gmail.com> - 2013-09-19 01:12 +1000
              Re: Language design William Ray Wing <wrw@mac.com> - 2013-09-18 12:58 -0400
                Re: Language design wxjmfauth@gmail.com - 2013-09-18 10:45 -0700
                Re: Language design Neil Cerutti <neilc@norwich.edu> - 2013-09-18 17:55 +0000
      Re: Language design Mark Janssen <dreamingforward@gmail.com> - 2013-09-13 17:28 -0700
      Re: Language design Vito De Tullio <vito.detullio@gmail.com> - 2013-09-14 07:25 +0200

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