Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.forth > #32974

Re: does VFX have the same bug as Gforth?

Show key headers only | View raw

Anton Ertl wrote:

> Bernd Paysan <bernd.paysan@gmx.de> writes:
>>Alex McDonald wrote:
>>> I would like to see that explained, since setting a single behaviour for
>>> IMMEDIATE words in my Forth has not caused any problems for me; and I
>>> struggle to see what code this might break. Can you give a concrete
>>> example?
>>
>>Ok, simple example:
>>
>>: cond, ( xt -- )  >r postpone IF r> compile, postpone THEN ;
>>: ?exit ( -- ) ['] exit cond, ; immediate
>>
>>Works fine when EXIT is not immediate - that's my assumption for now that
>>EXIT is non-immediate.
> 
> Just write it as
> 
> : cond, ( ct -- )  2>r postpone IF 2r> execute postpone THEN ;
> : ?exit ( -- ) [comp'] exit cond, ; immediate
> 
> and it will work whether EXIT is immediate or not.  You may argue that
> [COMP'] is not standard, but neither is "['] exit".

They are non-standard on a different level. ['] EXIT is an ambiguous 
condition (i.e. non-standard, because there's no consent between different 
implementers), [COMP'] is non-standard, because it's using a Gforth 
extension, not even proposed for inclusion into a future standard, and 
probably facing difficulties to get in.  An ambiguous condition means that 
when you write that code, you depend on an environmental restriction, and 
it's non-portable, but it's still using standard words.

It's non-portable just like + with overflow is non-portable, because 
different machines could behave different on overflow.  A predictable, 
intuitive response of the system to this ambiguous condition is certainly 
preferred, and what's a "intuitive response" depends upon the author of the 
code using that construct - so this depends on the existing code base, and 
the mentality that we don't existing break code - at least not with the 
systems where it originally ran on.  The likelyhood that the existing code 
base depends on ['] EXIT to throw an error is zero (no code base ever 
depends on not compiling ;-), so it's very likely that the code out there 
that actually does use ['] EXIT wants an xt as result.  Something to 
COMPILE,, to be precise, because that's the only use of that xt which makes 
sense.

The way a standard process works means that we probably need to change the 
definition of COMPILE, because it no longer reflects a consent within the 
Forth community.  There's simply an ambiguous condition if you COMPILE, a 
word with "special compilation semantics".  This would be the first 
transition step.  After this is done, Anton still can say "I want COMPILE, 
to be equivalent to POSTPONE LITERAL POSTPONE EXECUTE", and has his say in 
the compiler he maintains, but it's no longer something standard.

And the fact that it is no longer standard is a consequence of the 
"normative Kraft des Faktischen" as a German philosopher put it (the 
normative force of the factual - that is the main driving force of roughly 
consent-based standards) - there *are* popular systems out there where this 
relation doesn't hold, and funny enough, the Forth system Anton and I 
maintain, is among them - but so far, only if you actually use the non-
standard extension SET-COMPILER or COMP: to break this assumption (which 
means there is no standard way to write a program that exhibits this non-
standard behavior of COMPILE,).  This is, because we don't break code, and 
if you have funny uses of the current Gforth model, you still can continue 
to use them.  We don't know how much fun you had with the dual-xt approach, 
but we won't break your code if you did.  Certainly not without a long 
enough period of warning.

If we make this extension standard (optional wordset, of course), then there 
is a standard way to break the original COMPILE, assumption, and that would 
be phase 2 of the long transition.

The first thing I want to do with COMPILE, however is to remove this stupid 
COMPILE, is compile-only restriction.  I can't find a Forth where this is 
really the case, all compile

: test [ ' + compile, ] ;

Anton's proposal how to resolve the backward compatibility solution is to 
invent a new name for this new COMPILE, so e.g. XT, might do better (which 
would be defined as "append the compilation semantics of the xt"), and 
define COMPILE, so that it indeed does the equivalent of POSTPONE LITERAL 
POSTPONE EXECUTE, maybe optimizing the common case (default compilation 
semantics).  But that approach breaks the "user-implemented text 
interpreter", which was the motivation of Mitch Bradley to introduce 
COMPILE, at all.  And the code that uses COMPILE, exactly that way also 
exists.

The change to COMPILE, I probably would suggest would be, in the proporsal 
with SET-COMPILER:

SET-COMPILER ( comp-xt -- )
modifies the compilation semantics of the last definition to execute comp-xt 
on compilation

comp-xt: ( i*x xt -- j*y )
performs the compilation semantics of xt.

COMPILE, ( xt -- )
If xt has a special compilation semantics set by SET-COMPILER, perform this 
special compilation semantics, otherwise append the execution semantics of 
xt (default compilation semantics).

That way it is clearly extending the current COMPILE, in a way that now xts 
can carry non-default compilation semantics - and it's non-ambiguous by 
itself (i.e. still well-defined).  And of course we need to say that the 
system has to document which words with special compilation semantics are 
actually implemented that way.

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

Back to comp.lang.forth | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-17 21:09 -0700
  Re: does VFX have the same bug as Gforth? Bee <forth@calcentral.com> - 2014-08-17 23:06 -0700
    Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-18 17:03 -0700
      Re: does VFX have the same bug as Gforth? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-08-18 22:19 -0400
      Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-19 09:14 +0000
        Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-08-19 15:23 +0200
          Re: does VFX have the same bug as Gforth? "Alex McDonald" <blog@rivadpm.com> - 2014-08-19 14:54 +0100
            Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-08-19 16:09 +0200
              Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-19 15:39 +0000
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-08-19 22:34 +0200
                Re: does VFX have the same bug as Gforth? "Alex McDonald" <blog@rivadpm.com> - 2014-08-19 23:29 +0100
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-08-20 23:06 +0200
                Re: does VFX have the same bug as Gforth? "Alex McDonald" <blog@rivadpm.com> - 2014-08-20 22:21 +0100
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-20 07:46 +0000
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-08-21 00:26 +0200
                Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-20 22:42 -0700
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-21 10:23 +0000
                Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-21 23:29 -0700
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-22 12:54 +0000
                Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-22 17:54 -0700
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-23 10:46 +0000
                Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-23 11:15 -0700
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-24 13:32 +0000
                Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-24 10:40 -0700
                Re: does VFX have the same bug as Gforth? Bee <forth@calcentral.com> - 2014-08-24 22:03 -0700
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-25 08:31 +0000
                Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-25 22:55 -0700
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-21 12:45 +0000
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-22 15:13 +0000
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-08-22 18:47 +0200
                Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-22 18:28 -0700
                Re: does VFX have the same bug as Gforth? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-08-23 04:44 -0400
                Re: does VFX have the same bug as Gforth? Coos Haak <chforth@hccnet.nl> - 2014-08-23 16:15 +0200
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-23 11:50 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-23 07:15 +0000
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-08-23 22:12 +0200
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-24 03:51 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-24 13:36 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-25 04:16 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-25 09:44 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-25 11:53 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 06:34 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-26 03:55 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 12:37 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-26 08:24 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 13:55 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-26 10:42 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 16:05 +0000
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-09-23 17:20 +0200
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-09-23 11:29 -0500
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-09-23 23:01 +0200
                Re: does VFX have the same bug as Gforth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-08-25 15:59 +0000
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 06:23 +0000
                Re: does VFX have the same bug as Gforth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-08-26 09:15 +0000
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 13:23 +0000
                Re: does VFX have the same bug as Gforth? Mark Wills <markwills1970@gmail.com> - 2014-08-26 01:41 -0700
                Re: does VFX have the same bug as Gforth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-08-26 09:32 +0000
                Re: does VFX have the same bug as Gforth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-08-26 09:43 +0000
                Re: does VFX have the same bug as Gforth? Mark Wills <markwills1970@gmail.com> - 2014-08-26 02:48 -0700
                Re: does VFX have the same bug as Gforth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-08-26 11:58 +0000
                Re: does VFX have the same bug as Gforth? Mark Wills <markwills1970@gmail.com> - 2014-08-26 05:20 -0700
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 12:30 +0000
                Re: does VFX have the same bug as Gforth? stephenXXX@mpeforth.com (Stephen Pelc) - 2014-08-25 14:15 +0000
                Re: does VFX have the same bug as Gforth? Mark Wills <markwills1970@gmail.com> - 2014-08-25 07:44 -0700
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-25 14:37 +0000
                Re: does VFX have the same bug as Gforth? stephenXXX@mpeforth.com (Stephen Pelc) - 2014-08-25 15:14 +0000
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-25 15:33 +0000
                Re: does VFX have the same bug as Gforth? Mark Wills <markwills1970@gmail.com> - 2014-08-26 01:56 -0700
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-26 04:16 -0500
                Re: does VFX have the same bug as Gforth? Mark Wills <markwills1970@gmail.com> - 2014-08-26 02:24 -0700
                Re: does VFX have the same bug as Gforth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-08-26 09:36 +0000
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 13:40 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-26 08:57 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 12:52 +0000
                Re: does VFX have the same bug as Gforth? stephenXXX@mpeforth.com (Stephen Pelc) - 2014-08-26 14:14 +0000
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 14:36 +0000
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-09-23 17:40 +0200
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-26 10:53 -0500
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-09-23 17:36 +0200
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-25 12:02 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 06:42 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-26 04:08 -0500
                Re: does VFX have the same bug as Gforth? stephenXXX@mpeforth.com (Stephen Pelc) - 2014-08-26 10:37 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-26 08:30 -0500
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-28 08:47 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-29 13:03 +0000
                Re: does VFX have the same bug as Gforth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-08-29 09:16 -0500
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 13:06 +0000
                Re: does VFX have the same bug as Gforth? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-08-26 07:36 -0400
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-09-23 17:28 +0200
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-24 09:48 +0000
                Re: does VFX have the same bug as Gforth? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-08-24 15:55 -0400
                Re: does VFX have the same bug as Gforth? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-08-24 15:55 -0400
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-25 08:26 +0000
                Re: does VFX have the same bug as Gforth? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-08-26 07:36 -0400
                Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-26 12:12 +0000
                Re: does VFX have the same bug as Gforth? Bernd Paysan <bernd.paysan@gmx.de> - 2014-09-23 17:45 +0200
                Re: does VFX have the same bug as Gforth? Mark Wills <markwills1970@gmail.com> - 2014-08-21 03:25 -0700
                Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-21 23:14 -0700
            Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-19 14:16 +0000
  Re: does VFX have the same bug as Gforth? Bee <forth@calcentral.com> - 2014-08-17 23:16 -0700
    Re: does VFX have the same bug as Gforth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-08-19 09:40 +0000
  Re: does VFX have the same bug as Gforth? Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2014-08-18 09:16 +0100
  Re: does VFX have the same bug as Gforth? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-08-18 09:32 +0100
    Re: does VFX have the same bug as Gforth? "Alex McDonald" <blog@rivadpm.com> - 2014-08-18 13:09 +0100
  Re: does VFX have the same bug as Gforth? stephenXXX@mpeforth.com (Stephen Pelc) - 2014-08-18 12:29 +0000
    Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-18 17:10 -0700
      Re: does VFX have the same bug as Gforth? Bee <forth@calcentral.com> - 2014-08-18 17:48 -0700
        Re: does VFX have the same bug as Gforth? hughaguilar96@yahoo.com - 2014-08-18 18:23 -0700
      Re: does VFX have the same bug as Gforth? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-08-19 13:55 +0100

csiph-web