Date: Thu, 9 Jan 2025 17:15:24 +0100
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Subject: Re: "Back & Forth" - Local variables
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From: Hans Bezemer <the.beez.speaks@gmail.com>
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On 09-01-2025 13:42, dxf wrote:
>> There is no guarantee that a saved interpreter pointer on the
>> stack is an execution token.

Nope - in ANS-Forth it is listed as:

nest-sys; definition calls; implementation dependent

So - that's obvious. But in 4tH it works out. And defining it as >R 
works out as well. BTW, I've tested the thing - and it holds up.

I got my work cut out for a next episode! On co-routines! ;-)

Hans Bezemer

BTW, I've heard there are implementations where nest-sys aren't even on 
the return stack. The standard seems to confirm this:

return stack:  A stack that _MAY_BE_ used for program execution nesting, 
do-loop execution, temporary storage, and other purposes.

... and sorry to spoil the fun, but what we're doing here is illegal anyways:

"A program shall _NOT_ access values on the return stack (using R@, R>, 
2R@ or 2R>) that it _DID_NOT_ place there using >R or 2>R;"

In other words: your mileage may (be) very, very illegal.

Hans Bezemer