Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.arch > #4776

Re: implementation of unsigned addition on one's complement machines

Show all headers | View raw

nmm1@cam.ac.uk writes:
>In article <8503c9bb-07c6-4bae-ad8c-64f52322006c@g21g2000yqc.googlegroups.com>,
>Luca Forlizzi  <luca.forlizzi@gmail.com> wrote:
>>>
>>> >As you probably know, in C unsigned arithmetic is modular. This is
>>> >easily implemented in two's complement by ignoring the carry out of
>>> >addition.
>>>
>>> Division and remainder aren't.
>>
>>excuse me, do you mean that they are not modular or that the can not
>>be implemented by ignoring the carry out?
>
>There is no carry-out involved except, debatably, when dividing
>-(1+maxint) by -1 on a two's complete system.

That's not a division of unsigned numbers.  I don't think you can
produce an overflow with division (or remainder) of unsigned numbers
in C, so your mentioning of division does not contribute anything but
noise to the discussion.  Btw, wouldn't a C standards bigot write
(-maxint)-1 instead of -(1+maxint)?

- anton
-- 
M. Anton Ertl                    Some things have to be seen to be believed
anton@mips.complang.tuwien.ac.at Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html

Back to comp.arch | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

implementation of unsigned addition on one's complement machines Luca Forlizzi <luca.forlizzi@gmail.com> - 2011-11-14 07:08 -0800
  Re: implementation of unsigned addition on one's complement machines torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-11-14 17:55 +0100
    Re: implementation of unsigned addition on one's complement machines torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-11-15 10:29 +0100
      Re: implementation of unsigned addition on one's complement machines Luca Forlizzi <luca.forlizzi@gmail.com> - 2011-11-15 02:12 -0800
        Re: implementation of unsigned addition on one's complement machines nmm1@cam.ac.uk - 2011-11-15 10:28 +0000
          Re: implementation of unsigned addition on one's complement machines Luca Forlizzi <luca.forlizzi@gmail.com> - 2011-11-15 03:07 -0800
            Re: implementation of unsigned addition on one's complement machines nmm1@cam.ac.uk - 2011-11-15 11:13 +0000
              Re: implementation of unsigned addition on one's complement machines anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-15 17:33 +0000
                Re: implementation of unsigned addition on one's complement machines nmm1@cam.ac.uk - 2011-11-15 18:14 +0000
                Re: implementation of unsigned addition on one's complement machines anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-16 09:34 +0000
        Re: implementation of unsigned addition on one's complement machines Michael S <already5chosen@yahoo.com> - 2011-11-16 09:04 -0800
          Re: implementation of unsigned addition on one's complement machines nmm1@cam.ac.uk - 2011-11-16 17:31 +0000
          Re: implementation of unsigned addition on one's complement machines Robert Wessel <robertwessel2@yahoo.com> - 2011-11-16 11:54 -0600
    Re: implementation of unsigned addition on one's complement machines Luca Forlizzi <luca.forlizzi@gmail.com> - 2011-11-15 03:11 -0800
  Re: implementation of unsigned addition on one's complement machines anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-15 17:26 +0000
    Re: implementation of unsigned addition on one's complement machines Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-15 23:12 +0100
      Re: implementation of unsigned addition on one's complement machines Kai Harrekilde-Petersen <khp@harrekilde.dk> - 2011-11-15 23:25 +0100

csiph-web