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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.lang.forth
Subject: Re: single-xt approach in the standard
Date: Tue, 17 Sep 2024 19:25:39 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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Anthony Howe <achowe@snert.com> writes:
>On 2024-09-17 06:54, Ruvim wrote:
>> Do you think that the Forth standard should recognize the classic single-xt 
>> approach as possible for implementing a standard Forth system?
>> 
>> The classic single-xt approach implies that only one execution token (xt) is 
>> associated with a name token (nt), and only one name token is associated with a 
>> word (a named Forth definition). And words whose compilation semantics differ 
>> form default compilation semantics are implemented as immediate words.
>
>Given I prefer single-xt (currently), what I don't get is how for a dual-xt 
>system you define a single word with two actions for interpret and compile.

If you want the interpretation and compilation semantics,
NAME>INTERPRET gives you the interpretation semantics of the word, and
NAME>COMPILE gives you the compilation semantics.

>I 
>don't see a word to distinguish between the two, except maybe IMMEDIATE.

There is no standardized way to define words with arbitrary
combinations of interpretation and compilation semantics.  I don't
consider this to be a problem.  We would need such words only for
defining words like S", and we don't need additional words of this
kind.

If you want to see where going for full support for defining arbitrary
combinations leads, read our EuroForth 2019 paper [paysan&ertl19].

@InProceedings{paysan&ertl19,
  author =       {Bernd Paysan and M. Anton Ertl},
  title =        {The new {Gforth} Header},
  crossref =     {euroforth19},
  pages =        {5--20},
  url =          {http://www.euroforth.org/ef19/papers/paysan.pdf},
  url-slides =   {http://www.euroforth.org/ef19/papers/paysan-slides.pdf},
  video =        {https://wiki.forth-ev.de/doku.php/events:ef2019:header},
  OPTnote =      {refereed},
  abstract =     {The new Gforth header is designed to directly
                  implement the requirements of Forth-94 and
                  Forth-2012.  Every header is an object with a fixed
                  set of fields (code, parameter, count, name, link)
                  and methods (\texttt{execute}, \texttt{compile,},
                  \texttt{(to)}, \texttt{defer@}, \texttt{does},
                  \texttt{name>interpret}, \texttt{name>compile},
                  \texttt{name>string}, \texttt{name>link}).  The
                  implementation of each method can be changed
                  per-word (prototype-based object-oriented
                  programming).  We demonstrate how to use these
                  features to implement optimization of constants,
                  \texttt{fvalue}, \texttt{defer}, \texttt{immediate},
                  \texttt{to} and other dual-semantics words, and
                  \texttt{synonym}.}
}

@Proceedings{euroforth19,
  title = 	 {35th EuroForth Conference},
  booktitle = 	 {35th EuroForth Conference},
  year = 	 {2019},
  key =		 {EuroForth'19},
  url =          {http://www.euroforth.org/ef19/papers/proceedings.pdf}
}

>>   : s" ( "ccc" -- sd | )
>>     [char] " parse
>>     state @ if postpone sliteral exit then
>>     dup >r allocate throw tuck r@ move r>
>>   ; immediate

This definition does not implement the standard word CORE S" or FILE
S" (maybe if he redefined NAME>INTERPRET and NAME>COMPILE, and
consequently POSTPONE, and ', but he doesn't do that).

- 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: https://forth-standard.org/
   EuroForth 2024: https://euro.theforth.net