Re: Values and objects

From	Marko Rauhamaa <marko@pacujo.net>
Newsgroups	comp.lang.python
Subject	Re: Values and objects
Date	2014-05-11 18:10 +0300
Organization	A noiseless patient Spider
Message-ID	<87eh00s65j.fsf@elektro.pacujo.net> (permalink)
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Rustom Mody <rustompmody@gmail.com>:

> On Sunday, May 11, 2014 11:51:59 AM UTC+5:30, Marko Rauhamaa wrote:
>> Lisp variables (symbols) are on an equal footing with other objects.
>> IOW, lisp variables are objects in the heap.
>
> But is a symbol a variable??

Yes. A classic lisp symbol is even more "variable" than most other
variables! It can hold *two* values. One is called a value binding and
the other one the function binding. Scheme has unified the two; scheme
symbols have only one value binding, which can be a function.

> Sure, by providing a data-structure symbol, lisp provides one of the
> key building blocks for developing language processing systems.
>
> However I would argue that a variable is not a merely a symbol
> (identifier in more usual programming language-speak) but a relation
> between identifiers/symbols and some 'rhs'

The lisp symbol really is a data object with several fields: I can think
of name, value, function and properties. They can be accessed with
accessor functions. (Interestingly, scheme doesn't have the
'symbol-value accessor function of lisp's.)

If lisp didn't have a way to rebind symbols (i.e., if it were purely
functional and had no side effects), they wouldn't be so much variables
as substitution spots in the code.

> For an (interpreted?) language like python, rhs is naturally
> value/object For a C like language it is memory.

Symbols in lisp are memory slots, conceptually and physically.

Marko

Thread

Re: Pass variable by reference Ned Batchelder <ned@nedbatchelder.com> - 2014-05-06 16:31 -0400
  Re: Pass variable by reference Mark H Harris <harrismh777@gmail.com> - 2014-05-06 16:00 -0500
    Re: Pass variable by reference Ned Batchelder <ned@nedbatchelder.com> - 2014-05-06 17:27 -0400
    Re: Pass variable by reference Chris Angelico <rosuav@gmail.com> - 2014-05-07 09:46 +1000
      Re: Pass variable by reference Rustom Mody <rustompmody@gmail.com> - 2014-05-06 19:18 -0700
        Re: Pass variable by reference Chris Angelico <rosuav@gmail.com> - 2014-05-07 12:39 +1000
          Re: Pass variable by reference Rustom Mody <rustompmody@gmail.com> - 2014-05-06 19:54 -0700
            Re: Pass variable by reference Steven D'Aprano <steve@pearwood.info> - 2014-05-07 04:59 +0000
      Re: Pass variable by reference Mark H Harris <harrismh777@gmail.com> - 2014-05-07 13:11 -0500
        Re: Pass variable by reference Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 00:22 +0300
          Values and objects [was Re: Pass variable by reference] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 01:08 +0000
            Re: Values and objects [was Re: Pass variable by reference] Mark H Harris <harrismh777@gmail.com> - 2014-05-09 16:56 -0500
              Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-10 01:34 +0300
                Re: Values and objects Ben Finney <ben@benfinney.id.au> - 2014-05-10 10:24 +1000
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 01:01 +0000
                Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-09 19:19 -0700
                Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-10 12:33 +1000
                Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-09 20:05 -0700
                Re: Values and objects Mark H Harris <harrismh777@gmail.com> - 2014-05-09 23:15 -0500
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 06:15 +0000
                Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-10 17:21 +1000
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 09:09 +0000
                Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-10 19:32 +1000
                Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 12:10 -0700
                Re: Values and objects MRAB <python@mrabarnett.plus.com> - 2014-05-10 20:22 +0100
                Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 12:28 -0700
                Re: Values and objects Terry Reedy <tjreedy@udel.edu> - 2014-05-10 16:16 -0400
                Re: Values and objects Terry Reedy <tjreedy@udel.edu> - 2014-05-10 16:24 -0400
                Re: Values and objects Devin Jeanpierre <jeanpierreda@gmail.com> - 2014-05-10 14:03 -0700
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 03:17 +0000
                Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 13:30 +1000
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 05:11 +0000
                Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 15:22 +1000
                Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-10 22:31 -0700
                Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 09:21 +0300
                Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-10 23:48 -0700
                Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 18:10 +0300
                Re: Values and objects Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-05-11 11:26 +0300
                Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-11 01:48 -0700
                Re: Values and objects Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-05-11 15:22 +0300
                Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 18:46 +0300
                Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 22:56 +0300
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 12:51 +0000
                Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-11 07:12 -0700
                Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 22:42 -0700
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 06:40 +0000
                Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 09:18 +1000
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 03:11 +0000
                Re: Values and objects Rotwang <sg552@hotmail.co.uk> - 2014-05-11 14:46 +0100
                Re: Values and objects Ned Batchelder <ned@nedbatchelder.com> - 2014-05-11 14:40 -0400
                Re: Values and objects Rotwang <sg552@hotmail.co.uk> - 2014-05-12 00:06 +0100
                Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 18:28 -0700
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 07:24 +0000
                Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 11:59 +1000
                Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 07:29 +0000
                Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 21:46 -0700
                Re: [Python-Dev] Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 16:08 +1000
                Re: Values and objects albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-05-17 14:26 +0000
                Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-10 11:58 +1000
                Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-10 10:57 +0300
                Re: Values and objects Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-05-10 11:06 +0300
                Re: Values and objects Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-10 12:07 -0400
        Re: Pass variable by reference Chris Angelico <rosuav@gmail.com> - 2014-05-08 11:31 +1000
          Re: Pass variable by reference Mark H Harris <harrismh777@gmail.com> - 2014-05-09 17:30 -0500
            Abstractions [was Re: Pass variable by reference] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 00:58 +0000
              Re: Abstractions [was Re: Pass variable by reference] Mark H Harris <harrismh777@gmail.com> - 2014-05-09 21:17 -0500
  Re: Pass variable by reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-07 01:14 +0000

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