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Groups > comp.lang.forth > #33733

Re: Can every Forth do this?

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JennyB <jennybrien@googlemail.com> writes:
>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.

Should be possible everywhere, because EXECUTE needs to identify the
DOES> part in order to work.  Concerning "uniquely", in theory two
equal DOES> parts might have the same identity as far as EXECUTE is
concerned, but I doubt that any current Forth system does that
optimization.

>Is it also practical to derive n directly from the parent without creating a prototype child and then calling DOES ?

No, there may be several DOES> in a word, and CREATE and DOES> may be
in different words, and there may be several DOES> applied to the same
CREATEd word.  Even specifying what you want is probably difficult,
and even for a simple definition (where you only support one DOES> in
a word, and want to derive the definer from that) you incur additional
implementation cost whether that feature is used or not (you would
need an additional header field AFAICS).

- 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/

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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

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