Re: More on Boolean Shortcircuiting

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	Re: More on Boolean Shortcircuiting
Date	2012-06-01 12:45 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2012Jun1.144506@mips.complang.tuwien.ac.at> (permalink)
References	(3 earlier) <jq822d$4a8$1@dont-email.me> <m4wh3w.dn8@spenarnc.xs4all.nl> <jq9boh$tr7$2@dont-email.me> <LLednfSh5bB-71XSnZ2dnUVZ_gSdnZ2d@supernews.com> <89754066-11a1-4ac6-8e75-d0996abeb084@l5g2000vbo.googlegroups.com>

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Mark Wills <markrobertwills@yahoo.co.uk> writes:
>In .net we have TRY/CATCH/FINALLY which I always thought was very
>nice:
>
>Try
>  Code to try goes here
>Catch(ex)
>  Code to handle exception goes here.
>  Exception number passed in as ex
>Finally
>  Clean-up code goes here
>End Try

Gforth has:

|     TRY
|       code1
|       IFERROR
|         code2
|       THEN
|       code3
|     ENDTRY
|
|This performs code1.  If code1 completes normally, execution
|continues with code3.  If there is an exception in code1 or
|before @code{endtry, the stacks are reset to the depth during
|@code{try, the throw value is pushed on the data stack, and execution
|continues at code2, and finally falls through to code3.

code2 is the exception handling code and code3 is the cleanup code.

One advantage over using CATCH is that an exception in the cleanup
code (code3) will make execution containue right after code1.  While
this can lead to infinite loops if there is a bug in code2 or code3,
and one has to make sure that the data used by code2 and code3 is
preserved until the ENDTRY, for correct code it ensures that the
cleanup is always performed (while with CATCH-based solutions a Ctrl-C
at the wrong time can produce a nasty surprise.

OTOH, in the years since I implemented this, I have developed a much
higher opinion for xt-based interfaces like CATCH.  Maybe we can find
a way to do something like this TRY with an xt-based interface (but
currently I have no idea how).

- 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 2012: http://www.euroforth.org/ef12/

Thread

More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-26 09:39 +0000
  Re: More on Boolean Shortcircuiting Josh Grams <josh@qualdan.com> - 2012-05-26 12:44 +0000
    Re: More on Boolean Shortcircuiting Josh Grams <josh@qualdan.com> - 2012-05-26 12:47 +0000
      Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-26 14:16 +0000
    Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-26 13:48 +0000
      Re: More on Boolean Shortcircuiting Josh Grams <josh@qualdan.com> - 2012-05-27 00:17 +0000
  Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-26 08:27 -0700
    Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-26 10:25 -0700
      Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-27 10:47 +0000
        Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-27 07:00 -0700
          Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-27 17:20 +0000
            Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-27 15:03 -0700
  Re: More on Boolean Shortcircuiting "David N. Williams" <williams@umich.edu> - 2012-05-26 17:17 -0400
    Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-26 14:49 -0700
    Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-27 10:21 +0000
  Re: More on Boolean Shortcircuiting Josh Grams <josh@qualdan.com> - 2012-05-28 14:24 +0000
    Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-28 10:27 -0700
      Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-29 09:18 +0000
    Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-28 12:41 -0500
      Re: More on Boolean Shortcircuiting "Elizabeth D. Rather" <erather@forth.com> - 2012-05-28 07:55 -1000
    Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-29 11:34 +0000
    Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-29 13:53 +0000
      Re: More on Boolean Shortcircuiting Alex McDonald <blog@rivadpm.com> - 2012-05-29 07:02 -0700
        Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-30 01:45 +0000
          Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-29 20:02 -0700
            Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-30 04:27 +0000
              Re: More on Boolean Shortcircuiting Alex McDonald <blog@rivadpm.com> - 2012-05-30 02:09 -0700
                Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-30 11:07 +0000
                Re: More on Boolean Shortcircuiting Alex McDonald <blog@rivadpm.com> - 2012-05-30 04:38 -0700
                Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-30 06:46 -0500
                Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-30 13:52 +0000
                Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-30 09:02 -0500
                Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-30 14:13 +0000
                Re: More on Boolean Shortcircuiting Alex McDonald <blog@rivadpm.com> - 2012-05-30 07:41 -0700
                Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-30 11:46 -0500
                Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-31 09:18 -0700
                Re: More on Boolean Shortcircuiting Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-05-31 11:54 +0000
                Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-31 15:17 +0000
                Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-31 11:17 -0500
                Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-31 17:40 +0000
                Re: More on Boolean Shortcircuiting "Elizabeth D. Rather" <erather@forth.com> - 2012-05-31 08:43 -1000
                Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-06-01 02:56 +0000
                Re: More on Boolean Shortcircuiting anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-06-01 09:49 +0000
                Re: More on Boolean Shortcircuiting "Elizabeth D. Rather" <erather@forth.com> - 2012-06-01 09:18 -1000
                Re: More on Boolean Shortcircuiting Josh Grams <josh@qualdan.com> - 2012-05-31 16:45 +0000
                Re: More on Boolean Shortcircuiting BruceMcF <agila61@netscape.net> - 2012-05-31 09:58 -0700
                Re: More on Boolean Shortcircuiting Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-05-31 18:38 +0000
                Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-06-01 03:09 +0000
                Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-06-01 02:44 -0500
                Re: More on Boolean Shortcircuiting Mark Wills <markrobertwills@yahoo.co.uk> - 2012-06-01 04:57 -0700
                Re: More on Boolean Shortcircuiting anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2012-06-01 12:45 +0000
                Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-06-01 08:45 -0500
                Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-06-01 15:18 +0000
              Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-30 06:39 -0500
      Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-29 09:52 -0500
        Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-30 01:48 +0000
          Re: More on Boolean Shortcircuiting Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2012-05-30 07:55 +0100
          Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-30 02:56 -0500
            Re: More on Boolean Shortcircuiting Arnold Doray <invalid@invalid.com> - 2012-05-30 11:31 +0000
              Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-30 06:53 -0500
                Re: More on Boolean Shortcircuiting Alex McDonald <blog@rivadpm.com> - 2012-05-30 05:04 -0700
                Re: More on Boolean Shortcircuiting Andrew Haley <andrew29@littlepinkcloud.invalid> - 2012-05-30 09:03 -0500
      Re: More on Boolean Shortcircuiting Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2012-05-29 17:49 +0100
        Re: More on Boolean Shortcircuiting Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2012-05-29 19:06 +0100
      Re: More on Boolean Shortcircuiting Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-05-29 20:25 +0000

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