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Groups > comp.lang.forth > #57990

Re: mixed double and single signed division

From anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups comp.lang.forth
Subject Re: mixed double and single signed division
Date 2017-04-24 13:12 +0000
Organization Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID <2017Apr24.151206@mips.complang.tuwien.ac.at> (permalink)
References <bbcfd72a-4597-4839-aba0-3d4b98009995@googlegroups.com> <odh5gb$1j9o$1@gioia.aioe.org> <zY2dneeIGsT8u2HFnZ2dnUU7-V-dnZ2d@supernews.com> <f8a33236-78f6-462e-9bc1-67e2ca5c92b7@googlegroups.com>

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krishna.myneni@ccreweb.org writes:
>On Saturday, April 22, 2017 at 10:58:31 PM UTC-5, Elizabeth D. Rather wrote=
>:
>...
>>=20
>> FM/MOD and SM/REM came in with Forth94, as an attempt to compromise=20
>> between warring camps wanting to mandate either floored or symmetric=20
>> division, so weren't around at the time of Starting Forth.
>> ...
>
>
>It's also worth noting that FM/MOD and SM/REM have undefined behavior ("amb=
>iguous condition") when the quotient overflows a single length integer.

Note that an ambiguous condition in the Forth standard is more like
"implementation-defined" behaviour than "undefined behaviour" in the C
standard.  A standard system is required to document what happens on
undefined behaviour, and time-travel is not part of the Forth standard
(but it is part of the C standard).

>In =
>practice, on most Forth systems, I'm guessing that a program will fail sile=
>ntly, unless the program is specifically written to catch the overflow.

On IA-32 and AMD64, division overflow and dividing by zero produces a
CPU exception.  On a number of other CPUs, you just get some result.
Forth systems typically just do what the CPU does, but gforth (not
gforth-fast) produces a Forth exception for both conditions even on
CPUs where the hardware does not produce exceptions itself.

- 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 2016: http://www.euroforth.org/ef16/

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mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-22 08:21 -0700
  Re: mixed double and single signed division NN <november.nihal@gmail.com> - 2017-04-22 09:14 -0700
    Re: mixed double and single signed division NN <november.nihal@gmail.com> - 2017-04-22 09:22 -0700
      Re: mixed double and single signed division Coos Haak <htrofhc@gmail.com> - 2017-04-22 23:31 +0200
        Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-23 06:44 -0700
          Re: mixed double and single signed division hughaguilar96@gmail.com - 2017-04-23 13:24 -0700
      Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-23 06:41 -0700
        Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-23 13:29 -0700
  Re: mixed double and single signed division Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-22 11:40 -0500
    Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-23 06:52 -0700
  Re: mixed double and single signed division "HAA" <someone@microsoft.com> - 2017-04-23 13:02 +1000
    Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-22 17:58 -1000
      Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-23 13:36 -0700
        Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-23 16:33 -0700
          Re: mixed double and single signed division anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-24 13:23 +0000
            Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-24 18:49 -0700
        Re: mixed double and single signed division anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-24 13:12 +0000
          Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-24 18:35 -0700
            Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-24 15:52 -1000
              Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-25 02:18 -0700
              Re: mixed double and single signed division Paul Rubin <no.email@nospam.invalid> - 2017-04-25 02:25 -0700
                Re: mixed double and single signed division anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-25 11:30 +0000
                Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-25 08:08 -1000
                Re: mixed double and single signed division anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-26 14:48 +0000
            Re: mixed double and single signed division anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-25 08:40 +0000
              Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-25 02:25 -0700
                Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-25 03:00 -0700
                Re: mixed double and single signed division anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-25 11:37 +0000
                Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-25 05:27 -0700
                Re: mixed double and single signed division anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-25 13:34 +0000
                Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-25 15:29 -0700
                Re: mixed double and single signed division "HAA" <someone@microsoft.com> - 2017-04-27 14:02 +1000
                Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-27 16:00 -0700
                Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-27 19:20 -1000
                Re: mixed double and single signed division "HAA" <someone@microsoft.com> - 2017-04-28 22:41 +1000
            Re: mixed double and single signed division Coos Haak <htrofhc@gmail.com> - 2017-04-25 15:32 +0200
              Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-25 15:22 -0700
    Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-23 06:55 -0700
      Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-23 13:30 -1000
        Re: mixed double and single signed division krishna.myneni@ccreweb.org - 2017-04-23 16:45 -0700
        Re: mixed double and single signed division "HAA" <someone@microsoft.com> - 2017-04-24 10:56 +1000
          Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-23 15:06 -1000
            Re: mixed double and single signed division hughaguilar96@gmail.com - 2017-04-23 19:10 -0700
            Re: mixed double and single signed division Paul Rubin <no.email@nospam.invalid> - 2017-04-23 19:12 -0700
              Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-23 16:31 -1000
                Re: mixed double and single signed division hughaguilar96@gmail.com - 2017-04-23 21:17 -0700
                Re: mixed double and single signed division Paul Rubin <no.email@nospam.invalid> - 2017-04-23 21:47 -0700
                Re: mixed double and single signed division hughaguilar96@gmail.com - 2017-04-23 22:58 -0700
                Re: mixed double and single signed division hughaguilar96@gmail.com - 2017-04-23 23:22 -0700
                Re: mixed double and single signed division Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-24 04:46 -0500
            Re: mixed double and single signed division "HAA" <someone@microsoft.com> - 2017-04-24 12:59 +1000
              Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-23 18:03 -1000
                Re: mixed double and single signed division hughaguilar96@gmail.com - 2017-04-23 21:22 -0700
                Re: mixed double and single signed division "HAA" <someone@microsoft.com> - 2017-04-25 12:53 +1000
                Re: mixed double and single signed division "Elizabeth D. Rather" <erather@forth.com> - 2017-04-24 21:55 -1000
                Re: mixed double and single signed division "HAA" <someone@microsoft.com> - 2017-04-25 20:00 +1000

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