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Re: BEGIN with multiple AGAINs?

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From "Rod Pemberton" <dont_use_email@xnothavet.cqm>
Newsgroups comp.lang.forth
Subject Re: BEGIN with multiple AGAINs?
Date Sat, 14 Jun 2014 00:35:55 -0400
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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.
AFAIK, only ENTER/DOCOL does save a return stack value.  So, I don't
recognize an inherent flaw in my usage above "that would require
tail-call elimination".  I.e., if your statement is true, it must be
true of all Forths, in general, yes?

So, where does ANS say RECURSE has negative side effects? (stack overflow)

Doesn't your RECURSE DROP the stacked return address from ENTER/DOCOL?
Are you saying that me doing so in mine is incorrect?

This is mine.  It drops the stacked return address for ENTER/DOCOL.
It has no stack overflow.  It will RECURSE forever.  That's the
purpose of RECURSE, correct?  IMO, there is no point in using RECURSE
to nest repeatedly, say for a large sort or recursive algorithm, just
to overflow the return stack, especially when that is something fixable.
So, what's wrong with it, i.e., my (non-stack overflow) RECURSE ?

: RECURSE COMPILE R> COMPILE DROP LATESTXT @ +ofsCFA , ; IMMEDIATE

The XT is the start of my dictionary header which is not the
CFA hence +ofsCFA.  So, RECURSE compiles R> DROP and the XT of
the current word.

As you pointed out, if RECURSE does *NOT* DROP the stacked XT,
then you get a stack overflow.  AIUI, this should be true for all
Forths, whether interpreted or compiled, with or without an IF THEN,
i.e., not specifically due to my use above in the untested and
non-working example.

IMO, RECURSE is _useless_ if it doesn't DROP the ENTER/DOCOL return
stack address.  It will overflow, eventually, depending on stack size.


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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