Simplified automatic scoping (was: uninitialized ...)

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	Simplified automatic scoping (was: uninitialized ...)
Date	2014-10-08 16:06 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2014Oct8.180623@mips.complang.tuwien.ac.at> (permalink)
References	(5 earlier) <2014Oct7.173637@mips.complang.tuwien.ac.at> <svadnTUPuZtd0anJnZ2dnUU7-fWdnZ2d@supernews.com> <2014Oct8.145606@mips.complang.tuwien.ac.at> <V8udnS1fUb2WpqjJnZ2dnUU7-I-dnZ2d@supernews.com> <2014Oct8.173212@mips.complang.tuwien.ac.at>

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anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
>Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>>Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
>>> The benefit of defining a local where it is properly initialized is
>>> that every read from the local produces a proper value.  You cannot
>>> read the uninitialized value.
>>
>>I'm not going to argue with that advantage, but it's hard to do that
>>if you're only allowed to define locals in one place.
>
>Lifting that restriction is not that hard.

I already discussed the code generation side of a simple
implementation of that idea in
<2014Oct7.173637@mips.complang.tuwien.ac.at>.  Concerning the
automatic scoping,
<http://www.complang.tuwien.ac.at/papers/ertl94l.ps.gz> shows a
somewhat elaborate and quite precise way of how to do this.  Here I
present a simpler approach:

The local is visible from the definition of the local until the end of
the colon definition.  That lets some locals live longer than
described in the paper above earlier proposal (and one could argue
that the local will then be visible in places where it should not be
visible), but compared to the current situation of defining all the
locals at the start and letting them all be visible during the whole
definition, it is still an improvement.

For standardizing, I would suggest allowing different visibility
variants, from something block-structure-like to the simple approach
above.  Yes, a weak standard is not nice, but at least in this case it
is something that shows up in compilation.

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2014: http://www.euroforth.org/ef14/

Thread

Re: Why smudge? hughaguilar96@yahoo.com - 2014-09-30 19:25 -0700
  Re: Why smudge? november.nihal@gmail.com - 2014-10-01 08:54 -0700
    Re: Why smudge? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-01 19:09 +0000
  Re: Why smudge? november.nihal@gmail.com - 2014-10-01 10:16 -0700
    Re: Why smudge? hughaguilar96@yahoo.com - 2014-10-01 18:54 -0700
  Re: Why smudge? hughaguilar96@yahoo.com - 2014-10-02 15:31 -0700
    Re: Why smudge? Michael Barry <barrym95838@yahoo.com> - 2014-10-02 16:35 -0700
      Re: Why smudge? hughaguilar96@yahoo.com - 2014-10-02 17:02 -0700
        Re: Why smudge? Michael Barry <barrym95838@yahoo.com> - 2014-10-02 17:51 -0700
          Re: Why smudge? hughaguilar96@yahoo.com - 2014-10-02 18:50 -0700
        Re: Why smudge? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-10-04 00:30 +0100
          Re: Why smudge? hughaguilar96@yahoo.com - 2014-10-03 17:40 -0700
            Re: Why smudge? Raimond Dragomir <raimond.dragomir@gmail.com> - 2014-10-03 23:00 -0700
              Pelc's effort to sabotage cross-compiler writing has a work-around now! hughaguilar96@yahoo.com - 2014-10-04 21:14 -0700
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-05 03:42 -0500
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! Enoch <emc.consultants@gmail.com> - 2014-10-05 10:43 -0700
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! hughaguilar96@yahoo.com - 2014-10-05 20:21 -0700
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-06 03:58 -0500
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! hughaguilar96@yahoo.com - 2014-10-05 17:09 -0700
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! Michael Barry <barrym95838@yahoo.com> - 2014-10-06 11:15 -0700
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! hughaguilar96@yahoo.com - 2014-10-06 18:52 -0700
                More ranting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-07 03:48 -0500
                Re: More ranting albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-07 12:43 +0000
                Re: More ranting Bernd Paysan <bernd.paysan@gmx.de> - 2014-10-07 16:23 +0200
                Re: More ranting "Rod Pemberton" <buzzoff@nonamewhichexists.cmm> - 2014-10-16 01:03 -0400
                Re: More ranting Just Ian <superian@gmail.com> - 2014-10-16 07:14 -0700
                Re: More ranting Michael Barry <barrym95838@yahoo.com> - 2014-10-16 13:23 -0700
                uninitialized and implicitly initialized locals (was: More ranting) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-07 15:36 +0000
                Re: uninitialized and implicitly initialized locals (was: More ranting) Bernd Paysan <bernd.paysan@gmx.de> - 2014-10-07 22:15 +0200
                Re: uninitialized and implicitly initialized locals (was: More ranting) mhx@iae.nl - 2014-10-07 15:07 -0700
                Re: uninitialized and implicitly initialized locals (was: More ranting) Bernd Paysan <bernd.paysan@gmx.de> - 2014-10-08 03:11 +0200
                Re: uninitialized and implicitly initialized locals (was: More ranting) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-08 13:25 +0000
                Re: uninitialized and implicitly initialized locals (was: More ranting) hughaguilar96@yahoo.com - 2014-10-09 16:22 -0700
                Re: uninitialized and implicitly initialized locals (was: More ranting) "Rod Pemberton" <buzzoff@nonamewhichexists.cmm> - 2014-10-17 21:58 -0400
                Re: uninitialized and implicitly initialized locals (was: More ranting) mhx@iae.nl (Marcel Hendrix) - 2014-10-12 11:18 +0200
                Re: uninitialized and implicitly initialized locals (was: More ranting) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-08 12:35 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-07 15:27 -0500
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-08 12:56 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-08 08:24 -0500
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-08 15:32 +0000
                Simplified automatic scoping (was: uninitialized ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-08 16:06 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-08 11:57 -0500
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-08 12:18 -0500
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-09 14:19 +0000
                Re: uninitialized and implicitly initialized locals hughaguilar96@yahoo.com - 2014-10-09 14:42 -0700
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-09 14:07 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-09 10:44 -0500
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-10 16:03 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-10 13:35 -0500
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-11 10:53 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-12 11:34 -0500
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-15 12:44 +0000
                Re: uninitialized and implicitly initialized locals albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-15 14:34 +0000
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-15 15:03 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-15 11:10 -0500
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-16 12:19 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-17 03:56 -0500
                Re: uninitialized and implicitly initialized locals "Elizabeth D. Rather" <erather@forth.com> - 2014-10-17 07:48 -1000
                Re: uninitialized and implicitly initialized locals hughaguilar96@yahoo.com - 2014-10-17 19:26 -0700
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-18 12:55 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-18 13:21 -0500
                Re: uninitialized and implicitly initialized locals "Elizabeth D. Rather" <erather@forth.com> - 2014-10-18 08:44 -1000
                Re: uninitialized and implicitly initialized locals albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-19 09:53 +0000
                Re: uninitialized and implicitly initialized locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-20 12:48 +0000
                Re: uninitialized and implicitly initialized locals "Rod Pemberton" <buzzoff@nonamewhichexists.cmm> - 2014-10-20 16:24 -0400
                Re: uninitialized and implicitly initialized locals "Elizabeth D. Rather" <erather@forth.com> - 2014-10-20 10:30 -1000
                Re: uninitialized and implicitly initialized locals hughaguilar96@yahoo.com - 2014-10-20 16:23 -0700
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-26 04:16 -0500
                Re: uninitialized and implicitly initialized locals mhx@iae.nl (Marcel Hendrix) - 2014-10-26 11:32 +0200
                Re: uninitialized and implicitly initialized locals stephenXXX@mpeforth.com (Stephen Pelc) - 2014-10-26 14:27 +0000
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-26 13:56 -0500
                Re: uninitialized and implicitly initialized locals mhx@iae.nl (Marcel Hendrix) - 2014-10-26 20:32 +0200
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-26 16:18 -0500
                Re: uninitialized and implicitly initialized locals hughaguilar96@yahoo.com - 2014-10-26 15:05 -0700
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-26 17:53 -0500
                Re: uninitialized and implicitly initialized locals hughaguilar96@yahoo.com - 2014-10-26 16:30 -0700
                Re: uninitialized and implicitly initialized locals "Rod Pemberton" <buzzoff@nonamewhichexists.cmm> - 2014-10-27 01:45 -0400
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-27 12:21 -0500
                Re: uninitialized and implicitly initialized locals Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-10-26 17:57 -0500
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-10-06 20:55 +0100
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! hughaguilar96@yahoo.com - 2014-10-06 16:05 -0700
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-10-09 07:36 +0100
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! stephenXXX@mpeforth.com (Stephen Pelc) - 2014-10-10 01:52 +0000
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! hughaguilar96@yahoo.com - 2014-10-09 19:56 -0700
                Re: Pelc's effort to sabotage cross-compiler writing has a work-around now! "Rod Pemberton" <buzzoff@nonamewhichexists.cmm> - 2014-10-17 23:11 -0400
            Re: Why smudge? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-10-05 11:05 +0100
              Re: Why smudge? hughaguilar96@yahoo.com - 2014-10-05 19:48 -0700
                Re: Why smudge? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-10-06 07:53 +0100
                Re: Why smudge? "Elizabeth D. Rather" <erather@forth.com> - 2014-10-05 21:29 -1000
              Re: Why smudge? hughaguilar96@yahoo.com - 2014-10-09 15:16 -0700
              Re: Why smudge? "Rod Pemberton" <buzzoff@nonamewhichexists.cmm> - 2014-10-16 01:03 -0400

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