Path: csiph.com!eternal-september.org!feeder.eternal-september.org!nntp.eternal-september.org!.POSTED!not-for-mail
From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.forth
Subject: Re: dynamic scoping in Forth in one line of code
Date: Tue, 01 Sep 2026 17:15:12 -0700
Organization: A noiseless patient Spider
Lines: 15
Message-ID: <87ecfcld9r.fsf@nightsong.com>
References: <87bjamc5xh.fsf@debian> <nnd$4aef30ef$417a695d@6608074c8df9df23> <874igd9fjt.fsf@debian> <nnd$5e90e337$543815e0@6eeb63a0693c71c3> <875x0oa6fy.fsf@debian>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Injection-Date: Wed, 02 Sep 2026 00:15:13 +0000 (UTC)
Injection-Info: dont-email.me; logging-data="2415398"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19OY5w0G7H/lV0X6Wui+0JD"; posting-host="f76fb290cf12d7a8e7a9ec222d0b2cb1"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux)
Cancel-Lock: sha1:jWMzu3BDuUE5A/qv0Sy8AOsjHI8= sha1:7D4BdYQj+nEiJOBzp7fwxdVbw0w= sha256:HoY6VjS2aIQ7hv43Mn+0/FGyT/IIca9ZQ/2GsOe3HAk= sha1:S9z2o7Nv52486YjFHiHc3V6YvrM= sha256:gR4plY24OBPeBmbGj4r/qLP2XQaerBOXB1iKQXTkJsw=
Xref: csiph.com comp.lang.forth:135518

Kragen Javier Sitaker <kragen@canonical.org> writes:
> I think you’ve internalized it sufficiently that it’s not surprising to
> you, but it was surprising to me when I encountered it a year and a half
> ago, at which point I’d been programming for 43 years and occasionally
> programming in Forth for 27 years.  Maybe I'm just a slow learner.

The idea has been in the literature for a long time (it's discussed at
length in Knuth vol. 1 from 1968), but I think it wasn't well understood
in the programming community til much more recently.  This might be of
interest:

https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/coroutines-philosophy/

CO is similar to Knuth's (TAOCP's) coroutine jump as explained in the
"Coroutine paradigms" section of the article, I think.