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Re: mixed double and single signed division

From Andrew Haley <andrew29@littlepinkcloud.invalid>
Subject Re: mixed double and single signed division
Newsgroups comp.lang.forth
References (3 earlier) <raKdnb7em9WBpGDFnZ2dnUU7-LXNnZ2d@supernews.com> <odjigo$18j3$1@gioia.aioe.org> <aYmdndPdrNkU0mDFnZ2dnUU7-YXNnZ2d@supernews.com> <87a876tuyt.fsf@nightsong.com> <ioCdncMS6-kX_mDFnZ2dnUU7-b_NnZ2d@supernews.com>
Message-ID <gridnS75ffb6VGDFnZ2dnUU7-N_NnZ2d@supernews.com> (permalink)
Date 2017-04-24 04:46 -0500

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Elizabeth D. Rather <erather@forth.com> wrote:
> On 4/23/17 4:12 PM, Paul Rubin wrote:
>> "Elizabeth D. Rather" <erather@forth.com> writes:
>>> Which ones have you encountered in your work?
>>
>> This happens all the time.  Like it's currently April (the 4th month of
>> the year) and suppose you want to know what month it was 6 months ago.
>> With floored mod, (4-6) mod 12 is 10, so it was October.  With signed
>> mod, it was the month -2, which is less informative.
> 
> If I wanted to know that, there are many easier ways than computing it 
> that way. I'm looking for a real-world example, preferably one that 
> you've encountered.

The classic one is an angle of rotation, which can lead or lag and
sometimes even exceed 360 degrees, and I have encountered that in real
life.  But if the dividend is negative and all you want is the
remainder, all you have to do is add a multiple of the divisor into
the dividend.  The easiest way to do that is to add the dividend into
the high cell of the divisor and then do the division.

I believe that the argument circa 1981 was about whether MOD words
which can to handle negative dividends should be part of the standard
word set, rather that whether they were occasionally useful.  On the
other hand, I am happy to maintain that calculating the remainder of
anything mod N, N < 0 makes no sense.

Andrew.

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Thread

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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