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Groups > comp.lang.forth > #30534

Re: BEGIN with multiple AGAINs?

From rickman <gnuarm@gmail.com>
Newsgroups comp.lang.forth
Subject Re: BEGIN with multiple AGAINs?
Date 2014-05-21 17:11 -0400
Organization A noiseless patient Spider
Message-ID <llj4pd$uf4$1@dont-email.me> (permalink)
References <b16a0414-571d-4681-b405-68ad271124c7@googlegroups.com>

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On 5/21/2014 4:44 PM, David J wrote:
> Trying to think through Forth flow.  I have a situation where I need to call a succession of words, endlessly.  Each word returns a status (on the stack, of course).  This status is evaluated and either the next word in the list is called or else execution goes back to the BEGINning of the list.
>
> So, can an AGAIN be used in each IF ELSE test? Or a REPEAT?  Or is there a better way to handle this in Forth?

I would say what you are describing is a set of nested IF THEN clauses 
in structured programming terms.  I'm pretty sure you can't do this with 
multiple AGAIN words, but you should be able to define your own word(s) 
that allow you to implement something analogous to a CASE structure or 
maybe even adapt the CASE structure.

Remember that at compile time words like AGAIN consume the token on the 
stack that is used to define the jumps which make flow control work.

Another way I can think of doing this off the top of my head is to put 
the list in a word and exit the word to end the list...

: listword ( -- )
   word1 if exit then
   word2 if exit then
   .
   .
   .
   wordn drop ( or not )
;

You should be able to clean this up by writing a word that combines the 
semantics of "if exit then" into one word.

-- 

Rick

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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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