Re: RAFTS-like optimiser; progress report

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	Re: RAFTS-like optimiser; progress report
Date	2013-09-10 12:45 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2013Sep10.144553@mips.complang.tuwien.ac.at> (permalink)
References	(1 earlier) <LPqdnRhGztBg07fPnZ2dnUVZ_oadnZ2d@supernews.com> <2013Sep7.170614@mips.complang.tuwien.ac.at> <l0fpm9$i0g$1@dont-email.me> <2013Sep9.142330@mips.complang.tuwien.ac.at> <l0mu5m$old$1@dont-email.me>

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"Alex McDonald" <blog@rivadpm.com> writes:
>on 09/09/2013 13:23:31, anton wrote:
>> The cases I am thinking of have to do with fetching no-longer-changing
>> cells from a constant address. A simple example is an implementation
>> of CONSTANT with CREATE...DOES>:
>> 
>>: constant ( x -- )
>> create ,
>> does> ( -- x )
>> @ ;
>> 
>> 5 constant foo
>>: bla foo ;
>> bla .
>> 
>> The compiler cannot optimize the @ away in BLA, because one could
>> still do
>> 
>> 6 ' foo >body !
>> bla .
>
>My second reaction (actually, it may have been my first) was "EEEKK!!".
>Modifying a constant this way ranks just below 10 CONSTANT 5 .

Just because the defining word is called CONSTANT does not mean that
the compiler can assume that it behaves like the standard word
CONSTANT.  Consider:

: aword ( x -- )
 create ,
 does> ( -- x )
 @ ;
 
 5 aword foo
: bla foo ;
 bla .

and

: value ( x -- )
 create ,
 does> ( -- x )
 @ ;
 
 5 value foo
: bla foo ;
 bla .

The compiler cannot know the intent of the programmer and has to
assume that the program may change FOO later.

>This strikes me as not ANS Forth. Only the children of CREATE must have a
>body.  In my Forth, this blows up.

FOO is a child of CREATE, and this is a standard program.  If it blows
up in your compiler, your compiler has a bug.

- 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 2013: http://www.euroforth.org/ef13/

Thread

RAFTS-like optimiser; progress report Alex McDonald <blog@rivadpm.com> - 2013-09-06 14:12 -0700
  Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-06 16:54 -0500
    Re: RAFTS-like optimiser; progress report Alex McDonald <blog@rivadpm.com> - 2013-09-06 16:02 -0700
      Re: RAFTS-like optimiser; progress report Bernd Paysan <bernd.paysan@gmx.de> - 2013-09-07 03:01 +0200
        Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-07 03:21 -0500
          Re: RAFTS-like optimiser; progress report albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-09-07 19:56 +0000
    Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-07 15:06 +0000
      Re: RAFTS-like optimiser; progress report "Alex McDonald" <blog@rivadpm.com> - 2013-09-07 19:01 +0100
        Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-09 12:23 +0000
          Re: RAFTS-like optimiser; progress report "Alex McDonald" <blog@rivadpm.com> - 2013-09-10 12:01 +0100
            Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-10 12:45 +0000
              Re: RAFTS-like optimiser; progress report "Alex McDonald" <blog@rivadpm.com> - 2013-09-10 16:33 +0100
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-11 15:02 +0000
                Re: RAFTS-like optimiser; progress report "Alex McDonald" <blog@rivadpm.com> - 2013-09-11 17:44 +0100
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-13 11:58 +0000
                Re: RAFTS-like optimiser; progress report "Rod Pemberton" <dont_use_email@nohavenotit.com> - 2013-09-14 22:47 -0400
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-15 16:05 +0000
      Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-07 16:08 -0500
        Re: RAFTS-like optimiser; progress report mhx@iae.nl - 2013-09-08 03:21 -0700
          Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-08 06:42 -0500
            Re: RAFTS-like optimiser; progress report mhx@iae.nl - 2013-09-08 04:51 -0700
              Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-08 07:02 -0500
                Re: RAFTS-like optimiser; progress report Paul Rubin <no.email@nospam.invalid> - 2013-09-08 10:08 -0700
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-08 12:47 -0500
                Re: RAFTS-like optimiser; progress report Paul Rubin <no.email@nospam.invalid> - 2013-09-08 11:10 -0700
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-08 15:16 -0500
                Re: RAFTS-like optimiser; progress report Paul Rubin <no.email@nospam.invalid> - 2013-09-08 16:08 -0700
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-09 04:57 -0500
        Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-09 12:41 +0000
          Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-09 08:56 -0500
            Re: RAFTS-like optimiser; progress report albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-09-09 14:20 +0000
              Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-09 09:27 -0500
                Re: RAFTS-like optimiser; progress report "Rod Pemberton" <dont_use_email@nohavenotit.com> - 2013-09-10 04:31 -0400
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-10 05:11 -0500
            Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-09 15:08 +0000
              Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-09 10:45 -0500
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-11 15:21 +0000
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-11 12:04 -0500
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-11 17:46 +0000
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-11 14:45 -0500
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-13 13:00 +0000
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-13 10:46 -0500
                Re: RAFTS-like optimiser; progress report stephenXXX@mpeforth.com (Stephen Pelc) - 2013-09-13 17:44 +0000
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-14 15:31 +0000
                Re: RAFTS-like optimiser; progress report Paul Rubin <no.email@nospam.invalid> - 2013-09-14 10:33 -0700
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-14 12:39 -0500
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-15 15:05 +0000
                Re: RAFTS-like optimiser; progress report Alex McDonald <blog@rivadpm.com> - 2013-09-15 08:32 -0700
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-15 13:20 -0500
                Re: RAFTS-like optimiser; progress report stephenXXX@mpeforth.com (Stephen Pelc) - 2013-09-15 16:54 +0000
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-15 17:02 +0000
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-15 12:54 -0500
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-16 09:21 +0000
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-16 08:39 -0500
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-16 15:48 +0000
                Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-16 15:03 -0500
                Re: RAFTS-like optimiser; progress report anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-17 10:15 +0000
                Re: RAFTS-like optimiser; progress report "Rod Pemberton" <dont_use_email@nohavenotit.com> - 2013-09-17 17:24 -0400
                Re: RAFTS-like optimiser; progress report stephenXXX@mpeforth.com (Stephen Pelc) - 2013-09-17 13:10 +0000
            Re: RAFTS-like optimiser; progress report "Rod Pemberton" <dont_use_email@nohavenotit.com> - 2013-09-10 04:30 -0400
              Re: RAFTS-like optimiser; progress report Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-10 05:14 -0500
  Re: RAFTS-like optimiser; progress report mhx@iae.nl - 2013-09-07 03:22 -0700
  Re: RAFTS-like optimiser; progress report mhx@iae.nl - 2013-09-07 03:32 -0700

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