Re: LOOP

From	Gerry Jackson <do-not-use@swldwa.uk>
Newsgroups	comp.lang.forth
Subject	Re: LOOP
Date	2025-07-07 07:54 +0100
Organization	A noiseless patient Spider
Message-ID	<104fquq$2p8dc$1@dont-email.me> (permalink)
References	(6 earlier) <2025Jun28.122351@mips.complang.tuwien.ac.at> <1be678489d752a940e171d426000dc17ed1ac471@i2pn2.org> <103pht8$121l9$1@dont-email.me> <2025Jun28.230148@mips.complang.tuwien.ac.at> <f404de58a716f2f63cf31477da3014ae@www.novabbs.com>

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On 03/07/2025 20:33, minforth wrote:
> On Sat, 28 Jun 2025 21:01:48 +0000, Anton Ertl wrote:
> 
>> sean@conman.org writes:
>>>  What is the difference between FOR/NEXT and DO/LOOP?  Don't they do the
>>> same thing?
>>
>> FOR ... NEXT on one system does not do the same thing as FOR ... NEXT
>> on some other systems, and they all behave different from DO ... LOOP.
>>
> 
> Correct. Here are variants with iterators that even run on gforth 0.7.9:
> 
> \ ====== <n> FOR# .. #TIMES
> ==================================================
> \ original: machine code
> \ demo variant: slow Forth
> 
> : _ITERATE \ end xt
>      swap
>      BEGIN dup 0>
>      WHILE over execute 1-
>      REPEAT 2drop ;
> 
> : FOR# postpone [: ; IMMEDIATE
> 
> : #TIMES postpone ;] postpone _iterate ; IMMEDIATE
> 
> \ ====== <n> FOR .. N M .. NEXT
> ==============================================

I've found looping quotations useful but I like to include the quotation 
inside the loop e.g. (without the syntactic sugar and moving the 
iterator inside the quotation):

: downcount begin [: dup 0> if dup . 1- then ;] over 0> while execute 
repeat 2drop ;
10 downcount \ displays 10 9 8 7 6 5 4 3 2 1  ok

Advantages are:
1) The xt is not passed to the quotation and so doesn't get in the way. 
2) The xt is loaded as a literal when the quotation exits.
3) The quotation can exit the loop early by EXITing with 0 on the stack.

-- 
Gerry

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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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