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From: dxf <dxforth@gmail.com>
Newsgroups: comp.lang.forth
Subject: Re: Back & Forth - Co-routines
Date: Mon, 24 Mar 2025 12:50:58 +1100
Organization: i2pn2 (i2pn.org)
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On 23/03/2025 10:25 pm, Hans Bezemer wrote:
> On 23-03-2025 04:03, dxf wrote:
>> On 23/03/2025 2:51 am, sjack wrote:
>>> Ruvim <ruvim.pinka@gmail.com> wrote:
>>>
>>>> An artificial example:
>>>
>>> While wondering down roads less taken, I took a path where
>>> bacForth CUT: and -CUT were used in lieu of CATCH THROW .
>>
>> Does anyone have a reference/details for this anywhere as I can't seem to
>> find anything?
>>
>> A possibly useful hit but the doc is locked away:
>>
>> https://doi.org/10.1145/165628.165637
> 
> Found it! Try this one: https://www.complang.tuwien.ac.at/anton/euroforth/ef96/gassanenko96b.txt
> 
> But I'm gonna spoil it for you: BacForth has an extra "L" stack. CUT: and -CUT use it. You might wanna use this one if you REALLY want it: https://sourceforge.net/p/forth-4th/code/HEAD/tree/trunk/4th.src/lib/stack.4th
> 
> It's code for a light weight stack. BTW, TRACKING is missing as well. It might have to do with this one? https://sourceforge.net/p/forth-4th/code/HEAD/tree/trunk/4th.src/lib/backtrak.4th
> 
> : CUT:      \ mark the beginning of the fragment to cut
>     R>  RP@ >L                   \ copy r-stack top addr. to L-stack
>         BACK LDROP TRACKING      \ delete this mark when backtracking
>     >R ;
> : -CUT  R> L> RP! >R ;  \ delete return points upto the marked addr.
> : -NOCUT    \ remove the mark, but not the return points
>     R>
>       L> RP@ - >R                \ keep the mark as a relative address
>       BACK R> RP@ + >L  TRACKING \ restore it when backtracking
>     >R ;

Thank you (and sjack) for chasing down this one.  More detail appears to be
available in the SP-Forth sources directory:  \devel\~profit\lib\bac4th.f

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