From: dxforth@gmail.com   
      
   On 10/01/2025 3:15 am, Hans Bezemer wrote:   
   > On 09-01-2025 13:42, dxf wrote:   
   >>> There is no guarantee that a saved interpreter pointer on the   
   >>> stack is an execution token.   
      
   Albert said that.  He's referring to the use of EXECUTE.  What surprised me   
   is half the forths on my desktop worked (though not DX-Forth).   
      
   >   
   > 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! ;-)   
      
   Great.  While I've seen co-routines mentioned, examples were rare so I   
   tended to ignore it.   
      
   >   
   > 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.   
      
   The >R dependency is on what was (and perhaps still is) 'common practice'.   
   I was unsure how it would fare but all the popular forths seem to work.   
   If ANS-FORTH has issued one too many 'Thou shalt not's and in doing so has   
   excluded itself then that's too bad.   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)