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

Groups > comp.lang.forth > #33730 > unrolled thread

Can every Forth do this?

Back to article view | Back to comp.lang.forth

Contents

  Can every Forth do this? JennyB <jennybrien@googlemail.com> - 2014-10-07 07:33 -0700
    Re: Can every Forth do this? Roger Levy <roger.levy@gmail.com> - 2014-10-07 08:58 -0700
    Re: Can every Forth do this? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-07 16:16 +0000
      Re: Can every Forth do this? november.nihal@gmail.com - 2014-10-08 06:17 -0700
        Re: Can every Forth do this? Mark Wills <markwills1970@gmail.com> - 2014-10-08 09:55 -0700
        Re: Can every Forth do this? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-09 15:26 +0000
          Re: Can every Forth do this? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-10-09 19:42 +0100
    Re: Can every Forth do this? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-07 18:16 +0000
      Re: Can every Forth do this? Jason Damisch <jasondamisch@yahoo.com> - 2014-10-07 11:32 -0700
      Re: Can every Forth do this? Mark Wills <markwills1970@gmail.com> - 2014-10-07 14:27 -0700
        Re: Can every Forth do this? "Elizabeth D. Rather" <erather@forth.com> - 2014-10-07 13:38 -1000
          Re: Can every Forth do this? Mark Wills <markwills1970@gmail.com> - 2014-10-07 20:21 -0700
          Re: Can every Forth do this? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-08 11:33 +0000
            Re: Can every Forth do this? JennyB <jennybrien@googlemail.com> - 2014-10-08 06:25 -0700
              Re: Can every Forth do this? november.nihal@gmail.com - 2014-10-08 08:14 -0700
                Re: Can every Forth do this? Mark Wills <markwills1970@gmail.com> - 2014-10-08 10:10 -0700
                  Re: Can every Forth do this? JennyB <jennybrien@googlemail.com> - 2014-10-08 11:42 -0700
                    Re: Can every Forth do this? Roger Levy <roger.levy@gmail.com> - 2014-10-08 12:31 -0700
                      Re: Can every Forth do this? JennyB <jennybrien@googlemail.com> - 2014-10-09 07:03 -0700
                    Re: Can every Forth do this? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-08 19:33 +0000
                  Re: Can every Forth do this? november.nihal@gmail.com - 2014-10-08 16:39 -0700
                    Re: Can every Forth do this? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-08 23:45 +0000
            Re: Can every Forth do this? Harold <hzrabbie@gmail.com> - 2014-10-08 14:23 -0700
              Re: Can every Forth do this? "Elizabeth D. Rather" <erather@forth.com> - 2014-10-08 12:48 -1000
              Re: Can every Forth do this? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-08 23:39 +0000
          Re: Can every Forth do this? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-10-08 13:17 +0000
          Re: Can every Forth do this? Roger Levy <roger.levy@gmail.com> - 2014-10-08 07:33 -0700
            Re: Can every Forth do this? Roger Levy <roger.levy@gmail.com> - 2014-10-08 07:33 -0700
    Re: Can every Forth do this? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-10-07 20:23 +0100

Page 2 of 2 — ← Prev page 1 [2]

#33776

\\\

When I use counted strings, I prefer :- 

 count ==> ( str -- addr len ) where len is a byte range 0 .. 256 
lcount ==> ( str -- addr len ) where len is a cell range 0 .. 2^32-1

Also have 

wcount ==> ( str -- addr len ) where len is a cell range 0 .. 2^16-1  

But I tend to use lcount more often. 

[toc] | [prev] | [next] | [standalone]

#33777

In article <1e65cae9-b617-4a83-9938-a606d55dc904@googlegroups.com>,
 <november.nihal@gmail.com> wrote:
>\\\
>
>When I use counted strings, I prefer :-
>
> count ==> ( str -- addr len ) where len is a byte range 0 .. 256
>lcount ==> ( str -- addr len ) where len is a cell range 0 .. 2^32-1

>
>Also have
>
>wcount ==> ( str -- addr len ) where len is a cell range 0 .. 2^16-1

>
>But I tend to use lcount more often.

It is a bad idea to have 8 16 32 or 64 bits for the string length.
It should be a cell and the word must be named $@ ("string-fetch").

I grant COUNT a place, but I've renamed it to $@-BD.
(That is BD for brain-damaged.)

Groetjes Albert
-- 
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst

[toc] | [prev] | [next] | [standalone]

#33772

On Wednesday, October 8, 2014 4:33:25 AM UTC-7, Albert van der Horst wrote:
> In article <YPudnUS6_47k5KnJnZ2dnUU7-cOdnZ2d@supernews.com>,

> Indeed in ciforth you would have
> 
> 9 CONSTANT nine
> ' nine >DFA @ .
> 9 OK
> 
> But that is because CONSTANT is defined in the standard and can be
> implemented evert which way.
> 
> If constant is defined in the above way, you can get from nine to 9
> by the phrase
> 
> ' nine >BODY @
> 
> which is AFAIK perfectly sound ISO Forth.
> 

No it's not according to Forth 94.

6.1.0550 >BODY 
	( xt -- a-addr )
An ambiguous condition exists if xt is not for a word defined via CREATE.

Since "nine" is defined via CONSTANT, it may or may not work

[toc] | [prev] | [next] | [standalone]

#33774

On 10/8/14 11:23 AM, Harold wrote:
> On Wednesday, October 8, 2014 4:33:25 AM UTC-7, Albert van der Horst wrote:
>> In article <YPudnUS6_47k5KnJnZ2dnUU7-cOdnZ2d@supernews.com>,
>
>> Indeed in ciforth you would have
>>
>> 9 CONSTANT nine
>> ' nine >DFA @ .
>> 9 OK
>>
>> But that is because CONSTANT is defined in the standard and can be
>> implemented evert which way.
>>
>> If constant is defined in the above way, you can get from nine to 9
>> by the phrase
>>
>> ' nine >BODY @
>>
>> which is AFAIK perfectly sound ISO Forth.
>>
>
> No it's not according to Forth 94.
>
> 6.1.0550 >BODY
> 	( xt -- a-addr )
> An ambiguous condition exists if xt is not for a word defined via CREATE.
>
> Since "nine" is defined via CONSTANT, it may or may not work
>

Well, per subsequent clarifications by the OP, being restricted to 
CREATE is not a problem. He just happened to pick CONSTANT as an example.

Cheers,
Elizabeth

-- 
==================================================
Elizabeth D. Rather   (US & Canada)   800-55-FORTH
FORTH Inc.                         +1 310.999.6784
5959 West Century Blvd. Suite 700
Los Angeles, CA 90045
http://www.forth.com

"Forth-based products and Services for real-time
applications since 1973."
==================================================

[toc] | [prev] | [next] | [standalone]

#33775

In article <31ffdcd7-7d37-4c10-8d00-aab2447dd3d9@googlegroups.com>,
Harold  <hzrabbie@gmail.com> wrote:
>On Wednesday, October 8, 2014 4:33:25 AM UTC-7, Albert van der Horst wrote:
>> In article <YPudnUS6_47k5KnJnZ2dnUU7-cOdnZ2d@supernews.com>,
>
>> Indeed in ciforth you would have
>>
>> 9 CONSTANT nine
>> ' nine >DFA @ .
>> 9 OK
>>
>> But that is because CONSTANT is defined in the standard and can be
>> implemented evert which way.
>>
>> If constant is defined in the above way, you can get from nine to 9
>> by the phrase
>>
>> ' nine >BODY @
>>
>> which is AFAIK perfectly sound ISO Forth.
>>
>
>No it's not according to Forth 94.
>
>6.1.0550 >BODY
>       ( xt -- a-addr )
>An ambiguous condition exists if xt is not for a word defined via CREATE.

>
>Since "nine" is defined via CONSTANT, it may or may not work

Look at the original post.
The question was about
: CONSTANT CREATE , DOES> @ ;

not about just any constant given in a Forth.
So nine is defined via CREATE and there is no ambiguous condition.

Groetjes Albert
-- 
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst

[toc] | [prev] | [next] | [standalone]

#33756

"Elizabeth D. Rather" <erather@forth.com> writes:
>On 10/7/14 11:27 AM, Mark Wills wrote:
>> The parent is the word that creates the child.
>>
>> : constant create , does> @ ;
>> 9 constant nine
>>
>> Constant is the parent of nine.
>>
>
>So, if the question is whether you can *always* get to CONSTANT from 
>nine, the answer is no.

No, that was not the question.  The two questions are about an
identifier for a does>, called n in the original posting; in an
implementation this could be the address of the code after the DOES>.
The first question is whether you could get at this identifier from
the child of a CREATE...DOES> word.  The second question was whether
you could get at it from the CREATE...DOES> word itself.

>In some implementations you could get to nine's 
>parent from its xt, but some implementations of CONSTANT compile 
>literals in place or do other things, so there is no xt.

This is not about some implementations of CONSTANT, this is about
CREATE...DOES> words, with one example being

: constant create , does> @ ;

You cannot get at this CONSTANT from NINE, but you can get at the
address of the code after the DOES>, because otherwise EXECUTE would
not work.

- 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/

[toc] | [prev] | [next] | [standalone]

#33759

Exactly, and what's more I think extending CREATE DOES> is inappropriate.  It shouldn't be confused with some kind of idea of a primitive form of OOP waiting to be enhanced, even though it's been called a form of object orientation (wince).  Don't extend it if you want to be compatible...

[toc] | [prev] | [next] | [standalone]

#33760

I take it back - do extend it if you re-implement in standard Forth so you can define the assumptions.

[toc] | [prev] | [next] | [standalone]

#33736

On 07/10/2014 15:33, JennyB wrote:
> I've often seen implementation-specific versions of this, or its equivalent, and wondered if there are any Forth where it is not practical:
>
>     DOES xt -- n
>     Where xt belongs to a word defined by
>      CREATE ... DOES>
>     n uniquely identifies its parent.
>
> Is it also practical to derive n directly from the parent without creating a prototype child and then calling DOES ?
> ..
>

I agree with Albert - I don't know what you're asking.

-- 
Gerry

[toc] | [prev] | [standalone]

Page 2 of 2 — ← Prev page 1 [2]

Back to top | Article view | comp.lang.forth

csiph-web