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	2016-01-10 15:31 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2016Jan10.163141@mips.complang.tuwien.ac.at> (permalink)
References	(4 earlier) <QZCdnZGO7fqj8A3LnZ2dnUU7-LednZ2d@supernews.com> <f22796c6-fe3b-4719-bcaa-40971e8183e5@googlegroups.com> <L8adnWOmEutqLw3LnZ2dnUU7-X-dnZ2d@supernews.com> <466e4fc1-66f3-4842-8350-55fa9c80fcdd@googlegroups.com> <0dqdnRdSHaEcwQzLnZ2dnUU7-bOdnZ2d@supernews.com>

Show all headers | View raw

"Elizabeth D. Rather" <erather@forth.com> writes:
>On 1/9/16 6:04 AM, Chris Curl wrote:
>> Elizabeth, I was and am talking about constructs like this:
>>
>> : some-loop
>>    begin do-whatever
>>       yyy if break then \ this then is simple!
>>       zzz if break then
>>       ccc if break then
>>       \ any number of other conditions with "break"
>>    again
>>    then do-more-whatever \ this then ... not so much
>> ;
>> I am talking about the then (or whatever other word you choose to
>> call it) after again that that needs to resolve ALL the breaks.
>
>That is easy to do providing you use BEGIN ... UNTIL or BEGIN ... WHILE 
>,,, REPEAT instead of DO, etc., and a CASE structure. Here's an example 
>from one of the problem sets in Forth Application Techniques:
>
>: ?WAY ( -- )
>    BEGIN KEY DUP
>       27 = NOT WHILE   \ Quit on ESCape key
>       DUP 32 OR        \ Set lowercase bit
>       CASE
>          [CHAR] i OF  UP  ENDOF
>          [CHAR] j OF  LEFT   ENDOF
>          [CHAR] k OF  HOME   ENDOF
>          [CHAR] l OF  RIGHT  ENDOF
>          [CHAR] m OF  DOWN   ENDOF
>          SWAP DUP 32 127 WITHIN IF EMIT 0 THEN
>       ENDCASE DROP CR
>    REPEAT DROP ;

This example exits on just one condition, so it's not an illustration
of a solution to the problem that Chris Curl describes.

>Simple enough. It's just trying to mix the DO structures with the 
>indefinite loops that causes trouble, and the simple solution is Don't 
>Do That.

Not sure who is trying to do that.  As for using WHILE to exit a DO
loop, the only differences from using it to exit a BEGIN loop is that
you have to use UNLOOP on the exiting branch, that you must use THEN
in all cases (while in a BEGIN loop one THEN is integrated into
REPEAT), and it's non-standard.  My guess is that Chris Curl finds
both variants disgusting, and people who like 

BEGIN ... WHILE ... UNTIL THEN

will also like

?DO ... WHILE ... LOOP ELSE UNLOOP THEN

- 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/

Thread

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

csiph-web