Re: Coroutines in Forth

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.forth
Subject	Re: Coroutines in Forth
Date	2026-04-05 17:16 -0700
Organization	A noiseless patient Spider
Message-ID	<874ilpaqp1.fsf@nightsong.com> (permalink)
References	<10qunhm$1nnbt$1@dont-email.me> <10qunq9$1nqbc$1@dont-email.me>

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Gerry Jackson <do-not-use@swldwa.uk> writes:
> I've never heard of protothreads let alone used them. Apparently they

They are basically a fancier version of Simon Tatham's preprocessor
scheme.  In fact I confused the two.  See:

  https://dunkels.com/adam/pt/index.html

> Thanks for the link, very interesting. According to that paper the
> Forth implementation in my first post is an asymmetric coroutine as
> are Lua coroutines which they justify in an appendix,

I think there's a big difference, which is that in Lua, you can call
something as a coroutine, and it can yield from several levels deep in
function calls and later resume where it left off.  Python originally
couldn't do that, but it gained the ability later.  It's how
asynchronous i/o works in Python.  It also lets you implement
multitasking, by having the tasks avoid any blocking operations and
yield frequently to not hog the cpu.

Forth also often implements something like that, with a cooperative
multitasker API where you PAUSE every so often, and communicate through
mailboxes rather than with return values.  It's equivalent though.

> For the first point, in my example data local to the parser is
> retained but in global variables. That can be made local by putting
> them in a separate wordlist. Using Forth local variables doesn't make
> sense when [:] is used. If it did make sense then local variable
> values wouldn't be retained.

Yes, in the C macro system you use static local variables, somewhatlike
Forth globals.

> The re-entry point has to be called by name. I would think that makes
> it more readable.

Does that mean the caller has to know where the coroutine returns from?
That's more bookkeeping.

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Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-05 23:25 +0100
  Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-05 23:30 +0100
    Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-05 17:16 -0700
      Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-06 19:58 +0100
        Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-22 11:13 -0700
          Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-22 22:05 +0200
      Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-07 13:23 +0200
  Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-06 13:51 +0200
    Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-06 22:20 +0100
      Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-07 13:35 +0200
        Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-07 20:55 +0100
          Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-08 12:34 +0200
            Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 12:32 +0100
          Re: Coroutines in Forth Stephen Pelc <stephen@vfxforth.com> - 2026-04-09 10:12 +0000
        Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-10 19:01 +0200
          Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-11 11:54 +1000
            Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-05-01 13:07 +0200
          Re: Coroutines in Forth peter <peter.noreply@tin.it> - 2026-04-11 09:49 +0200
          Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-11 22:03 +0200
            Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-12 12:49 +1000
              Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-12 12:13 +0200
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-12 17:39 +0200
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-13 10:54 +1000
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-13 19:24 +0200
              Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-12 13:48 +0200
              Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-13 12:13 +0200
              Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-22 11:18 -0700
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-23 11:13 +1000
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-23 12:37 +0200
                Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-24 10:36 -0700
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-25 12:12 +1000
                Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-24 23:31 -0700
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-25 10:45 +0200
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-25 22:06 +1000
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-25 15:11 +0200
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-26 13:33 +1000
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-26 16:28 +0200
                Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-25 21:46 -0700
                FP stack depth limitations (was: Coroutines in Forth) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-26 05:55 +0000
                Re: FP stack depth limitations Paul Rubin <no.email@nospam.invalid> - 2026-04-26 00:28 -0700
                Re: FP stack depth limitations dxf <dxforth@gmail.com> - 2026-04-26 19:55 +1000
                Re: FP stack depth limitations (was: Coroutines in Forth) peter <peter.noreply@tin.it> - 2026-04-26 09:57 +0200
                Re: FP stack depth limitations (was: Coroutines in Forth) albert@spenarnc.xs4all.nl - 2026-04-26 14:34 +0200
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-25 15:01 +0200
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-05-01 13:13 +0200
                Forth, C, hardware, and programming virtues (was: Coroutines in Forth) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 05:26 +0000
                Re: Forth, C, hardware, and programming virtues Paul Rubin <no.email@nospam.invalid> - 2026-04-24 23:55 -0700
                Re: Forth, C, hardware, and programming virtues anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 08:21 +0000
                Re: Forth, C, hardware, and programming virtues albert@spenarnc.xs4all.nl - 2026-04-25 11:27 +0200
                Re: Forth, C, hardware, and programming virtues Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-25 15:43 +0200
                Re: Forth, C, hardware, and programming virtues anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 17:21 +0000
                Re: Forth, C, hardware, and programming virtues dxf <dxforth@gmail.com> - 2026-04-26 15:21 +1000
                Re: Forth, C, hardware, and programming virtues Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-26 15:08 +0200
                Re: Forth, C, hardware, and programming virtues albert@spenarnc.xs4all.nl - 2026-04-26 00:34 +0200
                Re: Forth, C, hardware, and programming virtues Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-26 15:10 +0200
                locals (was: Coroutines in Forth) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 04:47 +0000
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-04-24 23:21 -0700
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 06:43 +0000
                Re: locals albert@spenarnc.xs4all.nl - 2026-04-25 11:43 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 10:22 +0000
                Re: locals peter <peter.noreply@tin.it> - 2026-04-25 16:07 +0200
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-25 17:38 +0200
                Re: locals albert@spenarnc.xs4all.nl - 2026-04-26 01:13 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-26 14:03 +0000
                Re: locals peter <peter.noreply@tin.it> - 2026-04-27 09:31 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-27 07:53 +0000
                Re: locals peter <peter.noreply@tin.it> - 2026-04-27 11:52 +0200
                Re: locals albert@spenarnc.xs4all.nl - 2026-04-26 00:51 +0200
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-04-25 22:40 -0700
                Re: locals albert@spenarnc.xs4all.nl - 2026-04-26 14:55 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-26 09:50 +0000
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-26 16:22 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-26 17:04 +0000
                Re: locals dxf <dxforth@gmail.com> - 2026-04-27 11:51 +1000
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 08:21 +0200
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 08:22 +0200
                Re: locals dxf <dxforth@gmail.com> - 2026-04-27 11:12 +1000
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 14:34 +0200
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 14:34 +0200
                Re: locals Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-29 12:44 +0100
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-29 14:37 +0200
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-29 14:44 +0200
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-05-01 23:50 -0700
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-05-02 10:34 +0000
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-05-01 23:54 -0700
                Re: locals dxf <dxforth@gmail.com> - 2026-05-02 17:36 +1000
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-05-02 01:11 -0700
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-05-02 15:58 +0000
      Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-07 09:28 -0500
        Re: Coroutines in Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-07 16:12 +0000
          Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-07 18:06 -0500
          Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 11:43 +0100
            Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-08 13:16 +0200
              Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-08 11:47 -0500
                Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 21:48 +0100
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 07:06 -0500
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-09 16:41 +0200
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 13:34 -0500
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-10 01:23 +0200
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 21:34 -0500
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-09 13:01 +0200
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 07:01 -0500
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-09 16:10 +0200
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 13:29 -0500
              Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 21:26 +0100
          Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-08 14:22 +0200
          Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 15:31 +0200
            Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-29 10:49 +0200
              Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-29 15:22 +0200
        Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 11:33 +0100
          Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-08 13:07 +0200
            Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 22:05 +0100

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