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Re: BEGIN WHILE UNTIL THEN

From anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups comp.lang.forth
Subject Re: BEGIN WHILE UNTIL THEN
Date 2016-01-05 10:51 +0000
Organization Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID <2016Jan5.115120@mips.complang.tuwien.ac.at> (permalink)
References <08c4616c-21ad-4bdf-9fe4-a9e5ee2e5dad@googlegroups.com> <n6f2bj$qgs$1@gioia.aioe.org> <70db56dd-4768-4b8d-b94d-fb3200806866@googlegroups.com>

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Julian Fondren <julian.fondren@gmail.com> writes:
>By normal I mean, not requiring me to drop the pretense of
>structured programming, not requiring me to interpret these
>words as just performing conditional and unconditional GOTOs.

Actually, if you see this as one structure, it is structured
programming: It has one entrance and one exit.

>Personally, the benefits to this kind of programming aren't
>worth it.  It's too hard to understand.  It abuses the *names*
>of words.  THEN isn't THEN, really; it's just "resolve last
>forward branch".

It's a matter of getting used to.  I don't think that doing everything
that's possible (e.g., using ELSE to pair with WHILE) is a good idea,
but if you have multiple exit conditions, multiple WHILEs, or
WHILE...UNTIL are a common pattern.  I.e.,

BEGIN ... WHILE ... WHILE ... WHILE ... AGAIN THEN THEN THEN
BEGIN ... WHILE ... WHILE ... WHILE ... UNTIL THEN THEN THEN

with one THEN for each WHILE.  I don't consider it a good idea to put
something between the THENs, because then you have to match the THEN
to the WHILE that jumps there.  Putting something between UNTIL and
the first then, as in the example does not require matching, so it's
still acceptable.

Of course we have also discussed other options in the past, such as
using EXIT or a generalized CASE, but despite Gforth having a
generalized CASE, I have not used it.  The uses are rare enough that I
would have to look up the words when needed; OTOH, the WHILE ... THEN
usage is discussed frequently enough here that I grok it even though I
prefer using EXIT myself.

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2015: http://www.rigwit.co.uk/EuroForth2015/

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BEGIN WHILE UNTIL THEN Julian Fondren <julian.fondren@gmail.com> - 2016-01-04 14:50 -0800
  Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-05 11:24 +1100
    Re: BEGIN WHILE UNTIL THEN Julian Fondren <julian.fondren@gmail.com> - 2016-01-04 16:47 -0800
      Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-05 12:17 +1100
      Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-05 10:51 +0000
        Re: BEGIN WHILE UNTIL THEN stephen@mpeforth.com (Stephen Pelc) - 2016-01-05 15:06 +0000
  Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-04 17:25 -0800
    Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-05 13:06 +1100
      Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-04 21:42 -0800
        Re: BEGIN WHILE UNTIL THEN rickman <gnuarm@gmail.com> - 2016-01-05 01:48 -0500
        Re: BEGIN WHILE UNTIL THEN Albert van der Horst <albert@spenarnc.xs4all.nl> - 2016-01-05 11:15 +0000
        Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-06 14:35 +1100
  Re: BEGIN WHILE UNTIL THEN Albert van der Horst <albert@spenarnc.xs4all.nl> - 2016-01-05 02:04 +0000
  Re: BEGIN WHILE UNTIL THEN Julian Fondren <julian.fondren@gmail.com> - 2016-01-04 18:37 -0800
    Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-04 19:17 -0800
    Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-05 11:10 +0000
    Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-06 15:02 +1100
  Re: BEGIN WHILE UNTIL THEN november.nihal@gmail.com - 2016-01-05 08:03 -0800
    Re: BEGIN WHILE UNTIL THEN november.nihal@gmail.com - 2016-01-05 08:07 -0800
      Re: BEGIN WHILE UNTIL THEN november.nihal@gmail.com - 2016-01-05 08:18 -0800
      Re: BEGIN WHILE UNTIL THEN november.nihal@gmail.com - 2016-01-05 08:21 -0800
  Re: BEGIN WHILE UNTIL THEN Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-07 05:13 -0500
    Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-08 12:36 +1100
      Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-08 10:32 +0000
        Re: BEGIN WHILE UNTIL THEN Raimond Dragomir <raimond.dragomir@gmail.com> - 2016-01-08 02:55 -0800
          Re: BEGIN WHILE UNTIL THEN Coos Haak <chforth@hccnet.nl> - 2016-01-08 13:57 +0100
            Re: BEGIN WHILE UNTIL THEN Raimond Dragomir <raimond.dragomir@gmail.com> - 2016-01-08 06:55 -0800
              Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-08 15:06 -0800
              Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-08 16:59 -0800
                Re: BEGIN WHILE UNTIL THEN "Elizabeth D. Rather" <erather@forth.com> - 2016-01-08 16:15 -1000
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-08 22:23 -0800
                Re: BEGIN WHILE UNTIL THEN "Elizabeth D. Rather" <erather@forth.com> - 2016-01-08 21:12 -1000
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-09 08:04 -0800
                Re: BEGIN WHILE UNTIL THEN "Elizabeth D. Rather" <erather@forth.com> - 2016-01-09 09:16 -1000
                Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-10 15:31 +0000
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-10 08:11 -0800
                Re: BEGIN WHILE UNTIL THEN "Elizabeth D. Rather" <erather@forth.com> - 2016-01-10 09:42 -1000
                Re: BEGIN WHILE UNTIL THEN Albert van der Horst <albert@spenarnc.xs4all.nl> - 2016-01-11 13:02 +0000
                Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-13 16:20 +0000
                Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-10 14:10 -0800
                Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-11 18:38 -0800
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-14 08:47 +1100
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-13 17:24 -0800
                Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-13 19:25 -0800
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-14 22:09 +1100
                Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-14 16:21 +0000
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-16 11:34 +1100
                Re: BEGIN WHILE UNTIL THEN Bernd Paysan <bernd.paysan@gmx.de> - 2016-01-16 03:43 +0100
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-19 18:01 +1100
                Re: BEGIN WHILE UNTIL THEN Bernd Paysan <bernd.paysan@gmx.de> - 2016-01-19 23:07 +0100
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-21 14:29 +1100
                Re: BEGIN WHILE UNTIL THEN Bernd Paysan <bernd.paysan@gmx.de> - 2016-01-21 22:25 +0100
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-24 13:28 +1100
                Re: BEGIN WHILE UNTIL THEN Bernd Paysan <bernd.paysan@gmx.de> - 2016-01-25 01:31 +0100
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-25 21:45 +1100
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-25 10:24 -0800
                Re: BEGIN WHILE UNTIL THEN Bernd Paysan <bernd.paysan@gmx.de> - 2016-01-25 20:41 +0100
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-28 20:39 +1100
                Re: BEGIN WHILE UNTIL THEN Bernd Paysan <bernd.paysan@gmx.de> - 2016-01-28 16:05 +0100
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-21 20:52 -0800
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-24 13:16 +1100
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-14 08:46 -0800
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-16 11:34 +1100
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-15 20:53 -0800
                Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-13 19:31 -0800
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-11 09:29 +1100
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-10 21:18 -0800
                Re: BEGIN WHILE UNTIL THEN Paul Rubin <no.email@nospam.invalid> - 2016-01-10 21:29 -0800
                Re: BEGIN WHILE UNTIL THEN "Elizabeth D. Rather" <erather@forth.com> - 2016-01-10 20:37 -1000
                Re: BEGIN WHILE UNTIL THEN Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2016-01-11 09:05 +0000
                Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-12 12:26 +1100
                Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-10 14:18 -0800
                Re: BEGIN WHILE UNTIL THEN Raimond Dragomir <raimond.dragomir@gmail.com> - 2016-01-08 23:31 -0800
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-09 08:09 -0800
                Re: BEGIN WHILE UNTIL THEN Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-01-09 05:31 -0600
                Re: BEGIN WHILE UNTIL THEN Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-01-09 07:52 -0600
              Re: BEGIN WHILE UNTIL THEN Ron Aaron <rambamist@gmail.com> - 2016-01-09 18:22 +0200
              Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-09 16:29 +0000
          Re: BEGIN WHILE UNTIL THEN stephen@mpeforth.com (Stephen Pelc) - 2016-01-08 11:23 +0000
            Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-10 20:17 -0800
              Re: BEGIN WHILE UNTIL THEN stephen@mpeforth.com (Stephen Pelc) - 2016-01-11 11:56 +0000
              Re: BEGIN WHILE UNTIL THEN Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2016-01-11 11:59 +0000
                generalized CASE (was: BEGIN WHILE UNTIL THEN) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-11 12:30 +0000
                Re: generalized CASE (was: BEGIN WHILE UNTIL THEN) hughaguilar96@gmail.com - 2016-01-11 13:52 -0800
                Re: generalized CASE Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2016-01-11 22:00 +0000
                Re: generalized CASE Coos Haak <chforth@hccnet.nl> - 2016-01-12 01:50 +0100
                Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-11 14:16 -0800
                Re: BEGIN WHILE UNTIL THEN Chris Curl <ccurl609@gmail.com> - 2016-01-11 16:17 -0800
                Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-12 13:07 +0000
                Re: BEGIN WHILE UNTIL THEN Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2016-01-12 20:48 +0000
                Re: BEGIN WHILE UNTIL THEN hughaguilar96@gmail.com - 2016-01-12 14:16 -0800
          Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-08 16:21 +0000
            Re: BEGIN WHILE UNTIL THEN stephen@mpeforth.com (Stephen Pelc) - 2016-01-08 20:12 +0000
              Re: BEGIN WHILE UNTIL THEN anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-09 18:19 +0000
              Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-11 09:34 +1100
            Re: BEGIN WHILE UNTIL THEN Bernd Paysan <bernd.paysan@gmx.de> - 2016-01-08 21:13 +0100
        Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-09 23:46 +1100
      Re: BEGIN WHILE UNTIL THEN Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-08 10:11 -0500
        Re: BEGIN WHILE UNTIL THEN "HAA" <someone@microsoft.com> - 2016-01-11 08:38 +1100
  Re: BEGIN WHILE UNTIL THEN november.nihal@gmail.com - 2016-01-08 03:04 -0800

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