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Groups > comp.lang.forth > #43719 > unrolled thread

POSTPONE behaviour

Started byAliaksei Chapyzhenka <alex.drom@gmail.com>
First post2015-11-24 21:18 -0800
Last post2015-11-25 21:19 -0800
Articles 6 on this page of 46 — 11 participants

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  POSTPONE behaviour Aliaksei Chapyzhenka <alex.drom@gmail.com> - 2015-11-24 21:18 -0800
    Re: POSTPONE behaviour Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-11-24 22:00 -0800
      Re: POSTPONE behaviour Aliaksei Chapyzhenka <alex.drom@gmail.com> - 2015-11-24 22:15 -0800
        Re: POSTPONE behaviour Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-11-24 22:54 -0800
          Re: POSTPONE behaviour Aliaksei Chapyzhenka <alex.drom@gmail.com> - 2015-11-24 23:09 -0800
          Re: POSTPONE behaviour Lars Brinkhoff <lars.spam@nocrew.org> - 2015-11-25 08:15 +0100
            Re: POSTPONE behaviour Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-11-24 23:38 -0800
              Re: POSTPONE behaviour Lars Brinkhoff <lars.spam@nocrew.org> - 2015-11-25 08:46 +0100
                Re: POSTPONE behaviour Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-11-25 00:04 -0800
              Re: POSTPONE behaviour rickman <gnuarm@gmail.com> - 2015-11-25 03:01 -0500
                Re: POSTPONE behaviour Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-11-25 00:09 -0800
                  Re: POSTPONE behaviour rickman <gnuarm@gmail.com> - 2015-11-25 03:23 -0500
                    Re: POSTPONE behaviour Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-11-25 01:09 -0800
                      Re: POSTPONE behaviour rickman <gnuarm@gmail.com> - 2015-11-25 10:49 -0500
                        Re: POSTPONE behaviour "Elizabeth D. Rather" <erather@forth.com> - 2015-11-25 09:10 -1000
                  Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-11-25 09:18 +0000
                    Re: POSTPONE behaviour Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-11-25 02:21 -0800
                      Re: POSTPONE behaviour Mark Wills <markwills1970@gmail.com> - 2015-11-25 02:47 -0800
                      Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-11-25 13:58 +0000
                        Re: POSTPONE behaviour Mark Wills <markwills1970@gmail.com> - 2015-11-25 06:35 -0800
                          Re: POSTPONE behaviour Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-25 18:45 +0100
                        Re: POSTPONE behaviour Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-11-25 22:11 -0800
                          Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-11-26 07:42 +0000
                            Re: POSTPONE behaviour "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-11-26 05:20 -0500
                              Re: POSTPONE behaviour anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-26 16:50 +0000
                              Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-11-26 17:59 +0000
                                Re: POSTPONE behaviour Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-27 19:07 +0100
                                  Re: POSTPONE behaviour anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-28 11:24 +0000
                      Re: POSTPONE behaviour hughaguilar96@gmail.com - 2015-11-26 12:29 -0800
                        Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-11-27 09:53 +0000
                          Re: POSTPONE behaviour hughaguilar96@gmail.com - 2015-11-29 21:48 -0800
                            Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-11-30 12:18 +0000
                              Re: POSTPONE behaviour Lars Brinkhoff <lars.spam@nocrew.org> - 2015-11-30 13:41 +0100
                              Re: POSTPONE behaviour hughaguilar96@gmail.com - 2015-11-30 19:56 -0800
                                Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-12-01 09:59 +0000
                                  Re: POSTPONE behaviour hughaguilar96@gmail.com - 2015-12-01 22:46 -0800
                                    Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-12-02 07:50 +0000
                Re: POSTPONE behaviour anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-25 13:45 +0000
                  Re: POSTPONE behaviour rickman <gnuarm@gmail.com> - 2015-11-25 10:54 -0500
          Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-11-25 07:39 +0000
            Re: POSTPONE behaviour Aliaksei Chapyzhenka <alex.drom@gmail.com> - 2015-11-24 23:48 -0800
              Re: POSTPONE behaviour Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-11-25 08:03 +0000
      Re: POSTPONE behaviour Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-25 18:37 +0100
    Re: POSTPONE behaviour "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-11-25 01:27 -0500
      Re: POSTPONE behaviour Aliaksei Chapyzhenka <alex.drom@gmail.com> - 2015-11-24 22:51 -0800
    Re: POSTPONE behaviour Aliaksei Chapyzhenka <alex.drom@gmail.com> - 2015-11-25 21:19 -0800

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#43736

FromAliaksei Chapyzhenka <alex.drom@gmail.com>
Date2015-11-24 23:48 -0800
Message-ID<afdb9bd1-acb0-4b66-b63a-ae766e121665@googlegroups.com>
In reply to#43735
Looks like not much to read, (2 lines) ;)

https://cloud.githubusercontent.com/assets/511872/11388254/092617c4-92e9-11e5-9bfb-9e0c5433f12a.png

On Tuesday, November 24, 2015 at 11:39:37 PM UTC-8, Gerry wrote:
> On 25/11/2015 06:54, Raimond Dragomir wrote:
> >> But failing in this case:
> >> T{ : GT1 123 ; -> }T
> >> T{ : GT4 POSTPONE GT1 ; IMMEDIATE -> }T
> >> T{ : GT5 GT4 ; -> }T
> >> T{ GT5 -> 123 }T
> >
> > Well, think about it: GT4 is immediate. It is executed directly when you
> > define GT5. When executed it will call GT1 which leaves 123 on the data stack.
> >
> > So you already have 123 on the stack after GT5 definition.
> > Also, GT5 body is just a nop, because you compiled nothing (GT4 just
> > executed at compile time).
> > So when you lastly execute GT5 it will leave nothing (but you expect 123)
> >
> > Hope it helps
> >
> No, you're wrong. If you try it in GForth
> 
> : GT1 123 ;  ok
> : GT4 POSTPONE GT1 ; IMMEDIATE  ok
> : GT5 GT4 ;  ok
> gt5 . 123  ok
> see gt5
> : GT5
>    GT1 ; ok
> 
> GT4 compiles GT1 into the definition of GT5
> 
>  From your other post:
> 
>  > If the word postponed is not immediate, then postpone is redundant.
>  > .... FOO ... and
>  > .... POSTPONE FOO ... is the same thing if the FOO is not immediate.
> 
> is wrong too, POSTPONE is used for macros e.g.
> 
> : RDROP POSTPONE R> POSTPONE DROP ;
> : FOO RDROP ;  ok
> see RDROP
> : RDROP  [']
>    r> >comp ['] drop >comp ; immediate ok
> see FOO
> : FOO
>    r> drop ; ok
> 
> Read the ANS spec for POSTPONE carefully
> 
> -- 
> Gerry

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#43739

FromGerry Jackson <gerry@jackson9000.fsnet.co.uk>
Date2015-11-25 08:03 +0000
Message-ID<n33pra$3bn$1@dont-email.me>
In reply to#43736
On 25/11/2015 07:48, Aliaksei Chapyzhenka wrote:
> Looks like not much to read, (2 lines) ;)

The important bit is:

"...  Append the compilation semantics of name to the current 
definition. ..."

It doesn't distinguish between immediate and non-immediate words.

So if you have

: foo  postpone drop ; immediate
: bar foo ;

When BAR is being compiled FOO is executed because it is immediate and 
it compiles DROP into BAR because BAR is the "current definition".

>
> https://cloud.githubusercontent.com/assets/511872/11388254/092617c4-92e9-11e5-9bfb-9e0c5433f12a.png
>
> On Tuesday, November 24, 2015 at 11:39:37 PM UTC-8, Gerry wrote:
>> On 25/11/2015 06:54, Raimond Dragomir wrote:
>>>> But failing in this case:
>>>> T{ : GT1 123 ; -> }T
>>>> T{ : GT4 POSTPONE GT1 ; IMMEDIATE -> }T
>>>> T{ : GT5 GT4 ; -> }T
>>>> T{ GT5 -> 123 }T
>>>
>>> Well, think about it: GT4 is immediate. It is executed directly when you
>>> define GT5. When executed it will call GT1 which leaves 123 on the data stack.
>>>
>>> So you already have 123 on the stack after GT5 definition.
>>> Also, GT5 body is just a nop, because you compiled nothing (GT4 just
>>> executed at compile time).
>>> So when you lastly execute GT5 it will leave nothing (but you expect 123)
>>>
>>> Hope it helps
>>>
>> No, you're wrong. If you try it in GForth
>>
>> : GT1 123 ;  ok
>> : GT4 POSTPONE GT1 ; IMMEDIATE  ok
>> : GT5 GT4 ;  ok
>> gt5 . 123  ok
>> see gt5
>> : GT5
>>     GT1 ; ok
>>
>> GT4 compiles GT1 into the definition of GT5
>>
>>   From your other post:
>>
>>   > If the word postponed is not immediate, then postpone is redundant.
>>   > .... FOO ... and
>>   > .... POSTPONE FOO ... is the same thing if the FOO is not immediate.
>>
>> is wrong too, POSTPONE is used for macros e.g.
>>
>> : RDROP POSTPONE R> POSTPONE DROP ;
>> : FOO RDROP ;  ok
>> see RDROP
>> : RDROP  [']
>>     r> >comp ['] drop >comp ; immediate ok
>> see FOO
>> : FOO
>>     r> drop ; ok
>>
>> Read the ANS spec for POSTPONE carefully
>>
>> --
>> Gerry


-- 
Gerry

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#43764

FromBernd Paysan <bernd.paysan@gmx.de>
Date2015-11-25 18:37 +0100
Message-ID<n34rff$uvk$1@dont-email.me>
In reply to#43721
Raimond Dragomir wrote:

> POSTPONE lets you compile immediate words. Immediate words are executed at
> compile time, not compiled. Like the famous IF. IF will be executed at
> compile time. Your only chance to compile IF in a definition  is to
> POSTPONE it.
> 
> If the word postponed is not immediate, then postpone is redundant.
> ... FOO ... and
> ... POSTPONE FOO ... is the same thing if the FOO is not immediate.

Wow, clf is degrading fast.  Rod Pemberton posted something factually 100% 
correct (must be marked in the calendar ;-), and now this.

No, that's describing the effect of [COMPILE].

IMHO the easiest way to explain for newbees is the postpone mode with ]] foo 
bar [[.  If you have a word

: macro ]] foo bar [[ ; immediate

which in standard Forth is written

: macro  postpone foo  postpone bar ; immediate,

and you use that macro in another word like

: baz  macro ;

then you can think of inserting the words inside the double brackets or 
after postpone into baz, as if you wrote

: baz  foo bar ;

That works regardless if foo is immediate or not, so

: ?EXIT ]] IF  drop EXIT THEN [[ ; immediate

works fine.  Or with postpone:

: ?EXIT  postpone IF postpone drop postpone EXIT postpone THEN ; immediate

It's just more difficult to read with all the postpone clutter.

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
net2o ID: kQusJzA;7*?t=uy@X}1GWr!+0qqp_Cn176t4(dQ*
http://bernd-paysan.de/

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#43723

From"Rod Pemberton" <boo@fasdfrewar.cdm>
Date2015-11-25 01:27 -0500
Message-ID<op.x8m78dimyfako5@localhost>
In reply to#43719
On Wed, 25 Nov 2015 00:18:28 -0500, Aliaksei Chapyzhenka <alex.drom@gmail.com> wrote:

> I having trouble implementing POSTPONE word. Can someone help
> me with simple explanation of how POSTPONE works?

See my reply to someone else a few years back:
https://groups.google.com/d/msg/comp.lang.forth/RqN6h4qNlPs/RrktBeS62cUJ

Also, here are older c.l.f. threads with various implementations:
https://groups.google.com/d/msg/comp.lang.forth/nNTw9VjlSGU/Ab0Hvqm3jaUJ
https://groups.google.com/d/msg/comp.lang.forth/WfbirdJw1lE/VfaM4lp7y1AJ
https://groups.google.com/d/msg/comp.lang.forth/-SwXVMNhxHE/e4gQd634KwgJ


Rod Pemberton


-- 
How to kill Facebook.  Tell a bunch of fourth graders that
only old people use Facebook.  Wait eight years.

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#43727

FromAliaksei Chapyzhenka <alex.drom@gmail.com>
Date2015-11-24 22:51 -0800
Message-ID<58f65b1e-a92a-4e6b-a2ad-274b9db53f53@googlegroups.com>
In reply to#43723
Thank you Rod,
That sounds like great Thanks-Giving read!
--Alexey

On Tuesday, November 24, 2015 at 10:27:42 PM UTC-8, Rod Pemberton wrote:
> On Wed, 25 Nov 2015 00:18:28 -0500, Aliaksei Chapyzhenka <alex.drom@gmail.com> wrote:
> 
> > I having trouble implementing POSTPONE word. Can someone help
> > me with simple explanation of how POSTPONE works?
> 
> See my reply to someone else a few years back:
> https://groups.google.com/d/msg/comp.lang.forth/RqN6h4qNlPs/RrktBeS62cUJ
> 
> Also, here are older c.l.f. threads with various implementations:
> https://groups.google.com/d/msg/comp.lang.forth/nNTw9VjlSGU/Ab0Hvqm3jaUJ
> https://groups.google.com/d/msg/comp.lang.forth/WfbirdJw1lE/VfaM4lp7y1AJ
> https://groups.google.com/d/msg/comp.lang.forth/-SwXVMNhxHE/e4gQd634KwgJ
> 
> 
> Rod Pemberton
> 
> 
> -- 
> How to kill Facebook.  Tell a bunch of fourth graders that
> only old people use Facebook.  Wait eight years.

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#43798

FromAliaksei Chapyzhenka <alex.drom@gmail.com>
Date2015-11-25 21:19 -0800
Message-ID<a31dc552-3825-4524-a89a-886b5ea5cbc3@googlegroups.com>
In reply to#43719
Great Thanks to ALL of you!

Wow, insightful live discussion and elaborate explanations!
I especially love explanations from Gerry, Mark, Anton, Bernd and Elizabeth!
You have cracked an ice for me. Now I know how to fix my interpreter!

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