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Re: DO..LOOP and stack shuffling

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On 1/07/2025 9:53 pm, Hans Bezemer wrote:
> On 28-06-2025 19:46, Anton Ertl wrote:
>> And while DO has an obvious shortcoming (partially addressed by ?DO),
>> I have found that variations on ?DO..LOOP are quite helpful in keeping
>> the number of items on the data stack manageable.  They mean that I
>> don't have to deal with the index and limit in the loop body, and that
>> they are also out of the way, so I don't have to think about them in
>> the loop body.  And when I need the loop index, "I" gives it to me,
>> like an automatically-defined local. 
> 
> Wow.. I learned this about 20 years ago from the creator of the FIG Forth editor. You find it in the "c" and "delete" commands.
> 
> And yeah - you're completely right: it works like a "read-only" local.
> The TORS can be used as a "r/w" local - with the additional penalty of a R> >R pair (like 2OS comes with a SWAP SWAP penalty). BTW, knowing this gives you hints on how to organize your stacks.
> 
> The DO..LOOP advantages - nah, not really. E.g. an "address" loop can be done like (a n = address count):
> 
>   OVER SWAP /ELEMENT * + >R
>   BEGIN DUP R@ < WHILE ( ..) /ELEMENT + REPEAT R> DROP DROP
> 
> No need for BOUNDS DO..LOOP ..
> FOR..NEXT is even easier:
> 
>   >R BEGIN R@ 0> WHILE ( ..) R> 1- >R REPEAT R> DROP
> 
> So for a lot of applications, I don't really need DO..LOOP and its deeply flawed implementation. And since R@ and I are synonyms, I can even use I if I prefer I! :)
> ...

When I need a 'counted' loop DO LOOP is always shorter/faster than a BEGIN REPEAT.
I provide a couple FOR NEXTs in the distribution for the curious however they provide
no practical advantage (same footprint and in the case of CP/M even slower).  So for
me the issue was settled long ago.  I imagine it's the same for most forthers even if
their circumstances mean they've opted differently.

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OOS approach revisited zbigniew2011@gmail.com (LIT) - 2025-06-23 05:09 +0000
  Re: OOS approach revisited dxf <dxforth@gmail.com> - 2025-06-24 23:28 +1000
    Re: OOS approach revisited zbigniew2011@gmail.com (LIT) - 2025-06-26 17:27 +0000
      Re: OOS approach revisited minforth@gmx.net (minforth) - 2025-06-27 02:16 +0000
        Re: OOS approach revisited dxf <dxforth@gmail.com> - 2025-06-27 17:29 +1000
          Re: OOS approach revisited minforth <minforth@gmx.net> - 2025-06-27 11:49 +0200
            Re: OOS approach revisited zbigniew2011@gmail.com (LIT) - 2025-06-27 16:55 +0000
              Re: OOS approach revisited albert@spenarnc.xs4all.nl - 2025-06-27 20:15 +0200
                Re: OOS approach revisited minforth <minforth@gmx.net> - 2025-06-27 22:35 +0200
                Re: OOS approach revisited albert@spenarnc.xs4all.nl - 2025-06-28 11:34 +0200
                Re: OOS approach revisited Stephen Pelc <stephen@vfxforth.com> - 2025-06-28 09:37 +0000
              Re: OOS approach revisited dxf <dxforth@gmail.com> - 2025-06-28 12:03 +1000
            LOOP (was: OOS approach revisited) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2025-06-28 10:23 +0000
              Re: LOOP (was: OOS approach revisited) albert@spenarnc.xs4all.nl - 2025-06-28 14:26 +0200
              Re: LOOP dxf <dxforth@gmail.com> - 2025-06-28 22:41 +1000
                Re: LOOP sean@conman.org - 2025-06-28 20:04 +0000
                Re: LOOP anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2025-06-28 21:01 +0000
                Re: LOOP minforth@gmx.net (minforth) - 2025-07-03 19:33 +0000
                Re: LOOP Gerry Jackson <do-not-use@swldwa.uk> - 2025-07-07 07:54 +0100
                Re: LOOP minforth <minforth@gmx.net> - 2025-07-07 10:46 +0200
                Re: LOOP dxf <dxforth@gmail.com> - 2025-06-29 13:04 +1000
              Re: LOOP (was: OOS approach revisited) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2025-06-28 16:04 +0000
        DO..LOOP and stack shuffling (was: OOS approach revisited) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2025-06-28 17:46 +0000
          Re: DO..LOOP and stack shuffling Hans Bezemer <the.beez.speaks@gmail.com> - 2025-07-01 13:53 +0200
            Re: DO..LOOP and stack shuffling dxf <dxforth@gmail.com> - 2025-07-03 13:59 +1000
            Re: DO..LOOP and stack shuffling anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2025-07-03 07:50 +0000
        Re: OOS approach revisited Hans Bezemer <the.beez.speaks@gmail.com> - 2025-06-30 15:43 +0200
      Re: OOS approach revisited dxf <dxforth@gmail.com> - 2025-06-27 13:39 +1000

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