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Groups > comp.lang.forth > #31551

Re: BEGIN with multiple AGAINs?

From "Rod Pemberton" <dont_use_email@xnothavet.cqm>
Newsgroups comp.lang.forth
Subject Re: BEGIN with multiple AGAINs?
Date 2014-06-15 08:23 -0400
Organization Aioe.org NNTP Server
Message-ID <op.xhhwphzi6zenlw@localhost> (permalink)
References (3 earlier) <lne0l5$dt8$1@dont-email.me> <op.xhdvw1ao6zenlw@localhost> <lnen64$bdh$1@dont-email.me> <op.xhfgd5a66zenlw@localhost> <lngm60$7aj$1@dont-email.me>

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On Sat, 14 Jun 2014 01:22:22 -0400, rickman <gnuarm@gmail.com> wrote:
> On 6/14/2014 12:35 AM, Rod Pemberton wrote:
>> On Fri, 13 Jun 2014 07:27:00 -0400, Alex McDonald <blog@rivadpm.com>  
>> wrote:
>>> on 13/06/2014 09:15:59, "Rod Pemberton" wrote:

>>>> Isn't it time for a RECURSE LEAVE or EXIT ?
>>>> (untested, probably bad coding style jumping out of an IF ...)
>>>>
>>>> DUP @ IF EXECUTE CELL+ RECURSE THEN ;
>>>>
>>>
>>> That would require tail-call elimination for RECURSE THEN ;
>>> otherwise the return stack would grow uncontrollably.
>>
>> Why do you say that?
>>
>> IF and THEN don't put anything on the return stack, or shouldn't.
>
> RECURSE is a call so it pushes an address onto the return stack.

If you had read my post definition of RECURSE, you'd know or suspect
you didn't need to state that.

> Do you really not know that?

I do know that.  In fact, I said so.  It was the line that followed
the one above, which you snipped.  It's still the second line here:

RP> IF and THEN don't put anything on the return stack, or shouldn't.
RP> AFAIK, only ENTER/DOCOL does save a return stack value.

ENTER (or DOCOL) is what "pushes an address onto the return stack",
not RECURSE.  ENTER (or DOCOL) is what is stored in the CFA that
allows nesting of all high-level Forth words in an ITC Forth.

> That is why he says it should use tail call recursion to make
> it into a jump instead.

He said the return stack would grow uncontrollably here,
which it does with a (correctly) implemented RECURSE.

He responded afterwards by saying Andrew's example was correct,
but it demonstrates the exact same issue for the exact same
reason: RECURSE can overflow the return stack.

So, I see no bearing of your explanation here as to the issue at hand,
since his statement makes no sense.  The issue he cited is with Forth's
existing RECURSE, not my use of RECURSE, nor my incorrectly implemented
version of it.

>> IMO, RECURSE is _useless_ if it doesn't DROP the ENTER/DOCOL return
>> stack address.  It will overflow, eventually, depending on stack size.
>
> If RECURSE drops the value normally pushed onto the return stack then  
> you would only be able to use it at the *END* of a word.  What if the  
> use was in the middle?
>
> : EXAMPLE earlystuff  IF RECURSE THEN laststuff ;
>

Mine doesn't work there.  No, I hadn't re-tested it in a while.

> I can't believe you are really discussing this.

Well, you can go back to the non-Forth microprocessor threads, if you
don't like this one.  No one is forcing you to respond to me.

But, I think the issue of overflowing a stack with recursion isn't
inconsequential.  It's a serious hazard.

> In any other language RECURSE would just be a call to the routine
> being compiled.

It just seemed really flawed to me to allow a RECURSE that can't
actually RECURSE, i.e., call the same word forever.  In fact,
I added (and removed) the R> DROP to the definition multiple times.


Rod Pemberton

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Thread

BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-21 13:44 -0700
  Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-05-21 17:11 -0400
  Re: BEGIN with multiple AGAINs? mhx@iae.nl - 2014-05-21 14:31 -0700
    Re: BEGIN with multiple AGAINs? mhx@iae.nl - 2014-05-21 15:07 -0700
  Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-21 14:51 -0700
  Re: BEGIN with multiple AGAINs? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-05-21 21:59 +0000
  Re: BEGIN with multiple AGAINs? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-05-22 00:09 +0100
  Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-21 22:31 -0700
    Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-05-22 01:58 -0400
      Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-22 08:02 -0700
        Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-05-22 11:31 -0400
          Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-22 11:03 -0700
            Re: BEGIN with multiple AGAINs? forthisit@gmail.com - 2014-05-22 11:13 -0700
              Re: BEGIN with multiple AGAINs? forthisit@gmail.com - 2014-05-22 11:15 -0700
        Re: BEGIN with multiple AGAINs? forthisit@gmail.com - 2014-05-22 08:57 -0700
  Re: BEGIN with multiple AGAINs? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-22 13:47 +0000
  Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-22 11:27 -0700
    Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-22 11:38 -0700
    Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-05-22 14:47 -0400
      Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-22 12:22 -0700
  Re: BEGIN with multiple AGAINs? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-05-23 02:44 -0500
    Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-23 02:06 -0700
      Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-05-23 05:47 -0400
    Re: BEGIN with multiple AGAINs? "Elizabeth D. Rather" <erather@forth.com> - 2014-05-24 13:04 -1000
      Re: BEGIN with multiple AGAINs? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-05-25 15:06 -0500
        Re: BEGIN with multiple AGAINs? "Elizabeth D. Rather" <erather@forth.com> - 2014-05-25 16:37 -1000
          Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-05-25 23:56 -0400
          Re: BEGIN with multiple AGAINs? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-05-26 04:02 -0500
            Re: BEGIN with multiple AGAINs? "Elizabeth D. Rather" <erather@forth.com> - 2014-05-26 07:44 -1000
  Re: BEGIN with multiple AGAINs? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-05-23 12:39 -0700
  Re: BEGIN with multiple AGAINs? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-05-23 16:49 -0700
    Re: BEGIN with multiple AGAINs? Coos Haak <chforth@hccnet.nl> - 2014-05-24 02:00 +0200
  Re: BEGIN with multiple AGAINs? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-05-23 17:00 -0700
  Re: BEGIN with multiple AGAINs? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-05-23 21:29 -0700
    Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-24 08:10 -0700
      Re: BEGIN with multiple AGAINs? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-05-24 13:55 -0700
        Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-05-24 18:41 -0400
  Re: BEGIN with multiple AGAINs? Bee <forth@calcentral.com> - 2014-05-24 17:09 -0700
    Re: BEGIN with multiple AGAINs? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-05-24 18:05 -0700
      Re: BEGIN with multiple AGAINs? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-05-24 18:09 -0700
        Re: BEGIN with multiple AGAINs? ForthFreak <forthfreak@gmail.com> - 2014-05-25 02:03 -0700
          Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-05-25 05:18 -0400
            Re: BEGIN with multiple AGAINs? ForthFreak <forthfreak@gmail.com> - 2014-05-25 03:01 -0700
              Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-25 14:10 -0700
                Re: BEGIN with multiple AGAINs? "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2014-05-25 15:19 -0700
  Re: BEGIN with multiple AGAINs? Bee <forth@calcentral.com> - 2014-05-25 10:13 -0700
    Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-05-25 15:22 -0700
      Re: BEGIN with multiple AGAINs? BruceMcF <agila61@netscape.net> - 2014-06-12 13:11 -0700
        Re: BEGIN with multiple AGAINs? David J <skamolex@gmail.com> - 2014-06-12 19:06 -0700
  Re: BEGIN with multiple AGAINs? BruceMcF <agila61@netscape.net> - 2014-06-12 12:36 -0700
    Re: BEGIN with multiple AGAINs? BruceMcF <agila61@netscape.net> - 2014-06-12 19:50 -0700
      Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-06-13 01:02 -0400
        Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-13 04:16 -0400
          Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-06-13 05:22 -0400
            Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-14 00:33 -0400
              Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-06-14 01:15 -0400
              Re: BEGIN with multiple AGAINs? bruce.mcfarling@gmail.com - 2014-06-13 23:45 -0700
                Re: BEGIN with multiple AGAINs? bruce.mcfarling@gmail.com - 2014-06-14 00:00 -0700
          Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-06-13 05:26 -0400
            Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-14 00:32 -0400
          Re: BEGIN with multiple AGAINs? "Alex McDonald" <blog@rivadpm.com> - 2014-06-13 12:27 +0100
            Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-14 00:35 -0400
              Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-06-14 01:22 -0400
                Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-15 08:23 -0400
                Re: BEGIN with multiple AGAINs? BruceMcF <agila61@netscape.net> - 2014-06-15 11:57 -0700
                Re: BEGIN with multiple AGAINs? "Elizabeth D. Rather" <erather@forth.com> - 2014-06-15 09:13 -1000
              Re: BEGIN with multiple AGAINs? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-06-14 04:32 -0500
                Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-15 08:23 -0400
                Re: BEGIN with multiple AGAINs? "Alex McDonald" <blog@rivadpm.com> - 2014-06-15 19:20 +0100
              Re: BEGIN with multiple AGAINs? "Alex McDonald" <blog@rivadpm.com> - 2014-06-14 23:19 +0100
                Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-15 08:36 -0400
                Re: BEGIN with multiple AGAINs? "Alex McDonald" <blog@rivadpm.com> - 2014-06-15 19:18 +0100
                Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-26 18:34 -0400
                Re: BEGIN with multiple AGAINs? bruce.mcfarling@gmail.com - 2014-06-26 16:04 -0700
                Re: BEGIN with multiple AGAINs? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-06-15 19:27 +0000
              Re: BEGIN with multiple AGAINs? Mark Wills <markwills1970@gmail.com> - 2014-06-16 01:45 -0700
          Re: BEGIN with multiple AGAINs? BruceMcF <agila61@netscape.net> - 2014-06-13 09:14 -0700
            Re: BEGIN with multiple AGAINs? november.nihal@gmail.com - 2014-06-13 09:44 -0700
            Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-14 00:32 -0400
              Re: BEGIN with multiple AGAINs? bruce.mcfarling@gmail.com - 2014-06-13 23:25 -0700
        Re: BEGIN with multiple AGAINs? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-06-13 03:13 -0500
        Re: BEGIN with multiple AGAINs? BruceMcF <agila61@netscape.net> - 2014-06-13 08:38 -0700
          Re: BEGIN with multiple AGAINs? rickman <gnuarm@gmail.com> - 2014-06-13 13:29 -0400
            Re: BEGIN with multiple AGAINs? BruceMcF <agila61@netscape.net> - 2014-06-13 11:49 -0700
              Re: BEGIN with multiple AGAINs? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-06-14 00:41 -0400
                Re: BEGIN with multiple AGAINs? Elizabeth D Rather <erather@forth.com> - 2014-06-13 19:08 -1000
      Re: BEGIN with multiple AGAINs? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2014-06-13 21:27 +0100
  Re: BEGIN with multiple AGAINs? BruceMcF <agila61@netscape.net> - 2014-06-28 14:00 -0700

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