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From: Stephen Pelc <stephen@vfxforth.com>
Newsgroups: comp.lang.forth
Subject: Re: single-xt approach in the standard
Date: Tue, 17 Sep 2024 23:04:25 -0000 (UTC)
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On 17 Sep 2024 at 21:12:08 CEST, "Anthony Howe" <achowe@snert.com> wrote:

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

VFX Forth 64 is a single xt system (with sub-xts) . It manages to separate
compilation  and interpret actions for a word cleanly. S" is defined as below:

: S"            \ Comp: "ccc<quote>" -- ; Run: -- c-addr u      6.1.2165
\ *G Describe a string. Text is taken up to the next double-quote
\ ** character. The address and length of the string are returned.
  [char] " parse >syspad
;
ndcs: ( -- )  discard-sinline  compile (s") ",  ;

NDCS: describes the non-default compilation sematics of the word. The
process of arriving at this model is described in several recent EuroForth
papers.
-- 
Stephen Pelc, stephen@vfxforth.com
MicroProcessor Engineering, Ltd. - More Real, Less Time
133 Hill Lane, Southampton SO15 5AF, England
tel: +44 (0)78 0390 3612,  +34 649 662 974
http://www.mpeforth.com
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