Re: The current object

From	Bernd Paysan <bernd.paysan@gmx.de>
Newsgroups	comp.lang.forth
Subject	Re: The current object
Date	2013-05-14 18:37 +0200
Organization	1&1 Internet AG
Message-ID	<kmtp8h$iof$1@online.de> (permalink)
References	(19 earlier) <518b7d47$0$32115$14726298@news.sunsite.dk> <kmm6b0$9bd$1@online.de> <518f7fbb$0$32105$14726298@news.sunsite.dk> <kmrrtk$8nm$1@online.de> <_Lmdnbce8uElYQzMnZ2dnUVZ_sidnZ2d@supernews.com>

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Andrew Haley wrote:

> Bernd Paysan <bernd.paysan@gmx.de> wrote:
>> Note that this doesn't really work.  For the user of an object, it's
>> a black box (you can't access the ivars directly), but for derived
>> classes, it's a "grey box" - you *can* access the ivars.
> 
> IMO this is wrong -- it breaks encapsulation.  A subclass shouldn't
> access ivars any more than any other class.  (But, of course, I am not
> saying that a mechanism should prevent it, just that there's nothing
> special about subclasses.)

Really?  I think this is obsessive encapsulation, and probably originates in 
the "interface" concept:  You define an interface, which is a set of 
selectors.  And then you have various classes implementing that interface - 
as the interface itself does not have ivars, the classes don't share any 
ivars.  This concept is just one possible concept, it is a design choice 
when implementing your particular OOP system.  This doesn't mean it is a 
particular bad choice or so, but it is a choice.

> Sure, but it's harder than that because not only do people want a
> particular behaviour, they also insist on how it works internally.
> We'll never get anywhere unless people can relax that.

Yes.  But that follows a typical Forth tradition: that you don't encapsulate 
things.

However, this is not really impossible to solve in an OOP framework: The 
interface defines the behavior, and each class can implement it as it likes 
to.  The MOP would define the interface, and the actual object system would 
define the implementation.

So far, I've identified:

* People want different modes for sending messages - object on stack or not 
(Swoop actually already has these two modes, so this is not a new 
requirement).

* People want different modes for defining methods: current object, current 
object for ivars and object on stack for messages, or object on stack for 
both.  Or a "this" local variable instead of a current object...

* People are very performance sensitive, so they want to tune things.  Forth 
compilers are usually quite simple, so proposing invocation styles that 
require complex compilers (like trace schedulers) are not an option.

* We see "old and proven" arguments, which is the standard argument against 
any change.  Because it implies that "new" means "unproven".

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://bernd-paysan.de/

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The current object (was: Went open source with my GA144 ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-01 17:01 +0000
  Re: The current object (was: Went open source with my GA144 ...) albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-05-01 19:20 +0000
    Re: The current object (was: Went open source with my GA144 ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-02 17:02 +0000
  Re: The current object (was: Went open source with my GA144 ...) Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-02 02:12 +0200
    Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-02 04:52 -0400
    Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-02 04:31 -0500
      Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-02 18:25 +0200
        Re: The current object anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-02 16:58 +0000
          Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-02 22:26 +0200
            Re: The current object anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-06 14:52 +0000
              Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-07 03:47 +0200
                Re: The current object anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-07 15:22 +0000
        Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-02 12:12 -0500
          Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-02 21:56 +0200
            Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-03 03:19 -0500
            Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-03 06:54 -0400
    Re: The current object (was: Went open source with my GA144 ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-02 14:28 +0000
      Re: The current object (was: Went open source with my GA144 ...) Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-02 19:58 +0200
        Re: The current object (was: Went open source with my GA144 ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-03 16:50 +0000
          Re: The current object (was: Went open source with my GA144 ...) Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-04 18:58 +0200
            Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-04 13:35 -0500
              Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-05 01:08 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-04 18:29 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-05 03:00 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-05 03:48 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-05 23:15 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-06 05:01 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-07 03:23 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-07 03:39 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-07 19:00 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-07 13:34 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-07 22:00 +0200
                Re: The current object anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-08 07:26 +0000
                Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-05 06:39 -0400
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-05 09:15 -0500
                Re: The current object Paul Rubin <no.email@nospam.invalid> - 2013-05-05 09:25 -0700
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-05 11:43 -0500
                Re: The current object Paul Rubin <no.email@nospam.invalid> - 2013-05-05 09:59 -0700
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-06 05:06 -0500
                Re: The current object Mark Wills <forthfreak@gmail.com> - 2013-05-06 00:19 -0700
                Re: The current object "WJ" <w_a_x_man@yahoo.com> - 2013-05-13 22:45 +0000
                Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-05 06:39 -0400
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-05 23:40 +0200
            Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-05 06:39 -0400
              Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-05 23:29 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-06 05:10 -0500
                Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-08 07:35 -0400
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-09 00:06 +0200
                Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-09 06:41 -0400
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-11 21:31 +0200
                Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-12 07:40 -0400
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-14 01:10 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-14 03:58 -0500
                Re: The current object anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-14 14:51 +0000
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-15 03:48 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-14 18:37 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-14 14:42 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-15 00:22 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-15 02:56 -0500
                Re: The current object stephenXXX@mpeforth.com (Stephen Pelc) - 2013-05-15 13:52 +0000
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-15 17:58 +0200
                Re: The current object albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-05-17 14:01 +0000
                Re: The current object johno <email@address.com> - 2013-05-15 22:38 +0100
                Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-14 06:27 -0400
                Re: The current object albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-05-09 16:06 +0000
            Re: The current object (was: Went open source with my GA144 ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-06 16:12 +0000
              Re: The current object (was: Went open source with my GA144 ...) Alex McDonald <blog@rivadpm.com> - 2013-05-06 10:25 -0700
              Re: The current object (was: Went open source with my GA144 ...) Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-07 04:00 +0200
                Re: The current object (was: Went open source with my GA144 ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-07 15:02 +0000
              Re: The current object (was: Went open source with my GA144 ...) Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-07 04:09 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-07 03:41 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-07 19:02 +0200
                Re: The current object (was: Went open source with my GA144 ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-07 14:33 +0000
                Re: The current object (was: Went open source with my GA144 ...) Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-07 19:40 +0200
        Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-15 16:46 +0200
          Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-15 13:11 -0500
            Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-15 23:23 +0200
              Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-16 02:24 -0500
                Re: The current object anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-16 13:55 +0000
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-16 17:45 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-18 05:13 -0500
                Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-18 06:43 -0400
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-18 10:03 -0500
                Re: The current object Doug Hoffman <glidedog@gmail.com> - 2013-05-18 11:30 -0400
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-19 01:20 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-19 12:33 -0500
                Re: The current object Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-19 01:07 +0200
                Re: The current object Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-19 03:58 -0500
            OO dispatch (was: The current object) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-16 14:07 +0000
              Re: OO dispatch Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-18 05:28 -0500
                Re: OO dispatch anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-20 11:28 +0000
                Re: OO dispatch Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-20 09:00 -0500
                Re: OO dispatch Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-21 01:37 +0200
                Re: OO dispatch Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-21 03:21 -0500
                Re: OO dispatch anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-21 12:24 +0000
                Re: OO dispatch Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-21 10:18 -0500
                Re: OO dispatch anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-21 16:03 +0000
                Re: OO dispatch Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-05-21 12:55 -0500
                Re: OO dispatch Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-29 00:00 +0200
                Re: OO dispatch Mark Wills <markrobertwills@yahoo.co.uk> - 2013-05-28 15:49 -0700

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