generalized CASE (was: BEGIN WHILE UNTIL THEN)

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	generalized CASE (was: BEGIN WHILE UNTIL THEN)
Date	2016-01-11 12:30 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2016Jan11.133011@mips.complang.tuwien.ac.at> (permalink)
References	(3 earlier) <2016Jan8.113226@mips.complang.tuwien.ac.at> <d9ce8bc7-635a-4596-94f6-a29173edf95d@googlegroups.com> <568f9b94.1958323170@news.eternal-september.org> <ad7a5711-f46b-4362-ac85-166d82804be3@googlegroups.com> <n7059h$vai$1@dont-email.me>

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Gerry Jackson <gerry@jackson9000.fsnet.co.uk> writes:
>: of  ( dest #of -- orig #of+1 ) \ run-time ( x1 x2 -- | x1 )
>     >r
>     postpone over postpone = postpone if postpone drop
>     cs-swap r> 1+
>; immediate

The compile-time stack effect should be: 

( dest #of -- orig dest #of+1), as for ?OF.

It seems to me that the whole package would be slightly simpler if the
stack effect would be ( dest #of -- dest orig #of+1 ), and that of
ENDOF ( dest orig #of -- orig2 dest #of ).

>\ NEXTCASE loops back to CASE
>: nextcase  ( orig1 ... orign dest #of -- ) \ run-time ( x -- )
>     >r postpone drop postpone again r> resolve-origs
>; immediate

VFX also has NEXT-CASE (as well as an END-CASE) that does not expect
and drop the x.  I have a hard time coming up with loops where
NEXTCASE is more useful than NEXT-CASE, and if you use ?OF, END-CASE
seems more useful than ENDCASE.  However, I expect that the name
similarity to NEXTCASE/ENDCASE may confuse programmers and lead to
bugs.

In the Gforth sources we currently have DEFAULT: to deal with that: If
you don't use DEFAULT:, ENDCASE and NEXTCASE drop a value at run-time,
if you use DEFAULT:, they don't.  The idea is to use this in the
simplest case as:

CASE
  ... ?OF ... ENDOF
  ... ?OF ... ENDOF
  DEFAULT: defaultcode
ENDCASE

However, thinking about it again, this seems too roundabout, and we
are probably better off with

CASE
  ... ?OF ... ENDOF
  ... ?OF ... ENDOF
  defaultcode
0 ENDCASE

Of course the even better variant would be to only have END-CASE and
NEXT-CASE, and use DROP END-CASE instead of ENDCASE, but we now have
ENDCASE and have to live with it for a long time.  For the looping
variant, maybe we should go with NEXT-CASE only, though.

- 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

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