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Re: RfD: Quotations

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From Bernd Linsel <bl1@gmx.com>
Newsgroups comp.lang.forth
Subject Re: RfD: Quotations
Date Thu, 30 Jul 2015 12:38:58 +0200
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Am 30.07.2015 um 08:04 schrieb Paul Rubin:> Bernd Linsel <bl1@gmx.com> 
writes:
 >>> Perhaps it is clearer to require writing [: x y { x y } ...
 >> I'm still not lucky with this, while I reckon the copy-on-definition
 >> approach still sufficient.
 >
 > If I understand it, you're saying that at compile time, the { x y } in
 > the quotation should permanently allocate two cells in the global
 > dictionary.  Then on entry into the quotation, x and y from the parent
 > are pushed to the D stack, then popped to be stored in those two
 > dictionary cells.  Do I have that right?

That would be a clumsy realization, yes.

My example (and suggested syntax) is too complicated. I'll try again:

: bar { x y -- xt }
    [: x dup y + to x   + :] ;	\ locals not needed (but possible)

Accessing bar's x and y within the quotation makes them 'inherited' 
locals for the quotation and triggers copying them into the quotations' 
static frame.

This makes sure that a reference to them stays valid, even when bar's 
invocation ends and the original x and y cease to exist.

The downside of copying is that the quotation cannot alter bar's x or y, 
even if bar is still running.

 > What happens if multiple instances of the quotation are active at the
 > same time, like in a multitasking system?

Without locking, it would just be unpredictable which invocation of the 
quotation wins the contest who's writing x finally.
This problem arises likewise with full-fledged closure implementations 
(Lisp, SmallTalk, PostScript, JavaScript) with multitasking. As x can be 
written simultaneously, it should be regarded as shared resource, and 
safeguarded with appropriate lock mechanisms.

 > What happens if the quotation is recursive?

That's about the same. Nested function invocations with access to locals 
in stack frames 'above' them must be aware that they are shared.

 > Is burning two dictionary cells permanently really better than using
 > global variables?  Why not just push the inner locals onto the same
 > locals stack as the parent locals?

A quotation's inner locals (unrelated to its parent's locals) may be 
handled like any other local variables. It's just the 'inherited' ones 
that need special treatment if you want to allow access to them after 
the parent has exited -- what is what all my tattle is about...

--
Best regards
Bernd

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Thread

RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-28 21:22 +0100
  Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 07:35 +0000
    Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 14:20 +0100
  Re: RfD: Quotations Ron Aaron <rambamist@gmail.com> - 2015-07-29 13:44 +0300
    Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 13:42 +0100
  Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 05:35 -0700
    Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 13:34 +0000
      Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 07:35 -0700
        Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 15:05 +0000
        Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 16:19 +0100
          Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-29 21:48 +0100
      Re: RfD: Quotations mhx@iae.nl - 2015-07-29 11:13 -0700
        Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-30 13:04 +0000
    Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 15:07 +0100
      Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 07:44 -0700
        Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 15:12 +0000
        Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 16:18 +0100
          Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-29 18:37 +0200
            Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 17:55 +0100
              Re: RfD: Quotations "Elizabeth D. Rather" <erather@forth.com> - 2015-07-29 19:51 -0500
                Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 03:31 +0200
                Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 19:30 -0700
                Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 21:19 -0700
                Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 21:37 -0700
                Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-30 11:45 +0000
                Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-30 08:07 -0700
                Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-31 10:54 +0000
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 12:48 +0100
                Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-31 05:40 -0700
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 14:46 +0100
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 14:50 +0100
                Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-31 14:46 +0000
                Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-31 13:16 -0700
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 21:49 +0100
                Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 22:42 -0700
                Re: RfD: Quotations "Elizabeth D. Rather" <erather@forth.com> - 2015-07-30 08:46 -0500
                Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 21:40 -0700
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 10:01 +0100
                Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 12:00 +0200
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 11:10 +0100
                Re: RfD: Quotations Coos Haak <chforth@hccnet.nl> - 2015-07-30 16:35 +0200
            Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 16:53 +0000
          Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-29 19:03 +0200
            Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 18:24 +0100
              Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 01:38 +0200
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:10 +0100
                Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 12:06 +0200
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 11:21 +0100
                Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 14:00 +0200
                Re: RfD: Quotations franck.bensusan@gmail.com - 2015-07-30 06:59 -0700
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 10:53 +0100
            Re: RfD: Quotations Paul Rubin <no.email@nospam.invalid> - 2015-07-29 10:35 -0700
              Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 01:45 +0200
                Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 03:17 +0200
                Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 19:21 -0700
                Re: RfD: Quotations Paul Rubin <no.email@nospam.invalid> - 2015-07-29 23:04 -0700
                Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 12:38 +0200
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 12:09 +0100
                Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 13:26 +0200
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 09:47 +0100
                Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-31 02:51 -0700
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 11:21 +0100
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:11 +0100
            Re: RfD: Quotations Paul Rubin <no.email@nospam.invalid> - 2015-07-29 11:36 -0700
              Re: RfD: Quotations Paul Rubin <no.email@nospam.invalid> - 2015-07-29 11:37 -0700
            Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-30 13:07 +0000
              Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 16:25 +0200
          Re: RfD: Quotations mhx@iae.nl - 2015-07-29 11:16 -0700
            Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 20:27 +0100
              Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-29 21:57 +0100
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 22:48 +0100
                Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-31 12:34 +0100
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 13:00 +0100
                Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-31 14:31 +0000
                Re: RfD: Quotations mhx@iae.nl - 2015-07-31 11:32 -0700
              Re: RfD: Quotations mhx@iae.nl - 2015-07-29 21:42 -0700
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:57 +0100
          Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 17:21 -0700
            Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:56 +0100
              Re: RfD: Quotations franck.bensusan@gmail.com - 2015-07-30 04:15 -0700
                Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 12:30 +0100
                Re: RfD: Quotations franck.bensusan@gmail.com - 2015-07-30 05:04 -0700
                Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-30 13:07 -0700
  Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 16:52 -0700
    Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:53 +0100
  Re: RfD: Quotations Bernd Paysan <bernd.paysan@gmx.de> - 2015-07-30 21:45 +0200
    Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-30 13:25 -0700
      Re: RfD: Quotations Julian Fondren <ayrnieu@gmail.com> - 2015-07-30 15:11 -0700
        Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 09:11 +0100
          Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-31 12:04 +0100
    Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 22:51 +0100
      Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-30 22:38 -0700
        Re: RfD: Quotations "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-31 02:10 -0400
        Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 09:01 +0100
          Re: RfD: Quotations hughaguilar96@gmail.com - 2015-08-01 14:59 -0700
            Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-08-01 23:36 +0100
              Re: RfD: Quotations Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-02 01:19 +0200
                Re: RfD: Quotations hughaguilar96@gmail.com - 2015-08-01 18:27 -0700
                Re: RfD: Quotations hughaguilar96@gmail.com - 2015-08-09 14:34 -0700
  Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-31 08:52 +0000
    Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 11:57 +0100
  Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-31 21:42 +0100
    Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 22:25 +0100
      Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-31 23:39 +0100
        Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-08-01 10:59 +0100
    Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-01 14:18 +0000
      Re: RfD: Quotations Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-01 22:10 +0200
        Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-02 05:36 +0000
          Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-08-03 16:40 +0100
            Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-08-03 18:02 +0100
              Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-08-03 20:22 +0100
            Re: RfD: Quotations Coos Haak <chforth@hccnet.nl> - 2015-08-04 02:10 +0200
              Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-08-04 08:49 +0100
  Re: RfD: Quotations hughaguilar96@gmail.com - 2015-08-01 15:15 -0700

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