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Re: Best search algorithm to find condition within a range

Date 2015-04-09 09:19 -0400
From Dave Angel <davea@davea.name>
Subject Re: Best search algorithm to find condition within a range
References (4 earlier) <xurVw.125673$7_1.63712@fx15.am4> <87k2xlzknu.fsf@elektro.pacujo.net> <8738498qf7.fsf@dpt-info.u-strasbg.fr> <87fv89zd0m.fsf@elektro.pacujo.net> <87y4m1795n.fsf@dpt-info.u-strasbg.fr>
Newsgroups comp.lang.python
Message-ID <mailman.165.1428585562.12925.python-list@python.org> (permalink)

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On 04/09/2015 08:56 AM, Alain Ketterlin wrote:
> Marko Rauhamaa <marko@pacujo.net> writes:
>
>> Alain Ketterlin <alain@dpt-info.u-strasbg.fr>:
>>
>>> No, it would not work for signed integers (i.e., with lo and hi of
>>> int64_t type), because overflow is undefined behavior for signed.
>>
>> All architectures I've ever had dealings with have used 2's-complement
>> integers. Overflow is well-defined, well-behaved and sign-independent
>> wrt addition, subtraction and multiplication (but not division).
>
> You are confused: 2's complement does not necessarily mean modular
> arithmetic. See, e.g.,
> http://stackoverflow.com/questions/16188263/is-signed-integer-overflow-still-undefined-behavior-in-c
>

So the C standard can specify such things as undefined.  The 
architecture still will do something specific, right or wrong, and 
that's what Marko's claim was about.  The C compiler has separate types 
for unsigned and for signed, while the underlying architecture of every 
twos complement machine I have used did add, subtract, and multiply as 
though the numbers were unsigned (what you call modular arithmetic).

In my microcoding days, the ALU did only unsigned arithmetic, while the 
various status bits had to be interpreted to decide whether a particular 
result was overflow or had a carry.  It was in interpreting those status 
bits that you had to use the knowledge of whether a particular value was 
signed or unsigned.

Then the microcode had to present those values up to the machine 
language level.  And at that level, we had no carry bits, or overflow, 
or anything directly related.

-- 
DaveA

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Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 02:44 -0700
  Re: Best search algorithm to find condition within a range Dave Angel <davea@davea.name> - 2015-04-07 09:29 -0400
    Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 07:10 -0700
      Re: Best search algorithm to find condition within a range Dave Angel <davea@davea.name> - 2015-04-07 10:26 -0400
      Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-08 00:34 +1000
    Re: Best search algorithm to find condition within a range Denis McMahon <denismfmcmahon@gmail.com> - 2015-04-07 14:29 +0000
      Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 07:36 -0700
        Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-08 00:49 +1000
          Re: Best search algorithm to find condition within a range Grant Edwards <invalid@invalid.invalid> - 2015-04-07 15:05 +0000
            Re: Best search algorithm to find condition within a range Dave Angel <davea@davea.name> - 2015-04-07 11:23 -0400
            Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-08 01:37 +1000
            Re: Best search algorithm to find condition within a range MRAB <python@mrabarnett.plus.com> - 2015-04-07 17:02 +0100
        Re: Best search algorithm to find condition within a range MRAB <python@mrabarnett.plus.com> - 2015-04-07 16:00 +0100
          Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 08:43 -0700
            Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-08 08:51 +1000
              Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-08 11:46 +1000
        Re: Best search algorithm to find condition within a range Dave Angel <davea@davea.name> - 2015-04-07 11:04 -0400
        Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-07 09:06 -0600
          Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 08:47 -0700
            Re: Best search algorithm to find condition within a range Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-04-07 20:06 -0400
            Re: Best search algorithm to find condition within a range Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-04-08 12:49 +1200
        Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-08 08:36 +1000
          Re: Best search algorithm to find condition within a range Cameron Simpson <cs@zip.com.au> - 2015-04-08 08:51 +1000
        Re: Best search algorithm to find condition within a range Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-04-07 20:01 -0400
        Re: Best search algorithm to find condition within a range albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-04-18 18:08 +0000
          Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-19 23:02 +1000
            Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-19 17:56 +0300
              Re: Best search algorithm to find condition within a range Gene Heskett <gheskett@wdtv.com> - 2015-04-19 11:17 -0400
              Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-20 12:53 +1000
            Re: Best search algorithm to find condition within a range Dave Angel <davea@davea.name> - 2015-04-19 14:52 -0400
            Re: Best search algorithm to find condition within a range Paul Rubin <no.email@nospam.invalid> - 2015-04-19 13:44 -0700
            Re: Best search algorithm to find condition within a range albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-04-25 14:49 +0000
      Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 09:18 -0700
  Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-07 08:32 -0600
    Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 08:40 -0700
      Re: Best search algorithm to find condition within a range Dave Angel <davea@davea.name> - 2015-04-07 12:33 -0400
        Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 10:07 -0700
          Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-07 11:44 -0600
            Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-08 10:38 +1000
              Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-08 11:18 +1000
                Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-08 08:37 -0600
              Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 23:19 -0700
                Re: Best search algorithm to find condition within a range Mel Wilson <mwilson@the-wire.com> - 2015-04-08 13:39 +0000
                Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-08 07:56 -0700
                Re: Best search algorithm to find condition within a range Mel Wilson <mwilson@the-wire.com> - 2015-04-08 17:33 +0000
                Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-08 12:28 -0700
                Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-08 12:36 -0700
                Re: Best search algorithm to find condition within a range Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-04-08 21:28 +0100
                Re: Best search algorithm to find condition within a range Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-04-08 21:29 +0100
          Re: Best search algorithm to find condition within a range Terry Reedy <tjreedy@udel.edu> - 2015-04-07 14:55 -0400
          Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-07 13:19 -0600
            Re: Best search algorithm to find condition within a range Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-04-07 20:27 +0100
              Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 15:35 -0700
                Re: Best search algorithm to find condition within a range Dave Angel <davea@davea.name> - 2015-04-07 20:38 -0400
                Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-07 17:35 -0600
                Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-08 00:28 -0700
                Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-08 08:35 -0600
                Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-08 00:35 -0700
          Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-08 05:25 +1000
          Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-07 13:28 -0600
          Re: Best search algorithm to find condition within a range Serhiy Storchaka <storchaka@gmail.com> - 2015-04-07 23:57 +0300
          Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-08 10:18 +1000
            Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-08 07:31 +0300
      Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-07 14:15 -0600
      Re: Best search algorithm to find condition within a range Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-04-07 21:42 +0100
    Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-08 08:55 +1000
      Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-07 17:30 -0600
  Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-08 08:57 +1000
    Re: Best search algorithm to find condition within a range Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-04-08 12:59 +1200
      Re: Best search algorithm to find condition within a range Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-04-08 02:39 +0100
      Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 23:12 -0700
    Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-08 11:49 +1000
      Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-09 12:32 +1000
        Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-09 12:39 +1000
          Re: Best search algorithm to find condition within a range wxjmfauth@gmail.com - 2015-04-08 23:14 -0700
    Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-07 22:50 -0700
    Re: Best search algorithm to find condition within a range wxjmfauth@gmail.com - 2015-04-07 23:07 -0700
      Re: Best search algorithm to find condition within a range wxjmfauth@gmail.com - 2015-04-07 23:18 -0700
        Re: Best search algorithm to find condition within a range Denis McMahon <denismfmcmahon@gmail.com> - 2015-04-08 17:27 +0000
          Re: Best search algorithm to find condition within a range wxjmfauth@gmail.com - 2015-04-08 10:50 -0700
    Re: Best search algorithm to find condition within a range BartC <bc@freeuk.com> - 2015-04-08 22:22 +0100
      Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 01:06 +0300
        Re: Best search algorithm to find condition within a range Chris Kaynor <ckaynor@zindagigames.com> - 2015-04-08 17:01 -0700
        Re: Best search algorithm to find condition within a range BartC <bc@freeuk.com> - 2015-04-09 10:19 +0100
          Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 13:00 +0300
            Re: Best search algorithm to find condition within a range Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2015-04-09 13:57 +0200
              Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 15:45 +0300
                Re: Best search algorithm to find condition within a range Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2015-04-09 14:56 +0200
                Re: Best search algorithm to find condition within a range Dave Angel <davea@davea.name> - 2015-04-09 09:19 -0400
                Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 16:33 +0300
                Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 16:49 +0300
                Re: Best search algorithm to find condition within a range Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2015-04-09 15:57 +0200
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 00:08 +1000
                Re: Best search algorithm to find condition within a range Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2015-04-09 16:53 +0200
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 01:02 +1000
                Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-09 08:12 -0700
                Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-10 01:21 +1000
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 01:36 +1000
                Re: Best search algorithm to find condition within a range MRAB <python@mrabarnett.plus.com> - 2015-04-09 17:40 +0100
                Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-09 07:54 -0700
                Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-09 09:03 -0600
                Re: Best search algorithm to find condition within a range jonas.thornvall@gmail.com - 2015-04-09 08:21 -0700
                Re: Best search algorithm to find condition within a range Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-09 10:23 -0600
                Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-10 01:11 +1000
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 01:34 +1000
                Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-10 02:15 +1000
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 02:36 +1000
                Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-10 03:49 +1000
                Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 19:25 +0300
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 02:43 +1000
                Re: Best search algorithm to find condition within a range Grant Edwards <invalid@invalid.invalid> - 2015-04-09 16:53 +0000
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 03:00 +1000
                Re: Best search algorithm to find condition within a range Grant Edwards <invalid@invalid.invalid> - 2015-04-09 17:44 +0000
                Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-10 03:41 +1000
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 04:07 +1000
                Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 21:14 +0300
                Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 21:11 +0300
                Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 20:43 +0300
                Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-10 03:35 +1000
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 03:56 +1000
                Re: Best search algorithm to find condition within a range Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-10 23:18 +1000
                Re: Best search algorithm to find condition within a range Chris Angelico <rosuav@gmail.com> - 2015-04-10 23:41 +1000
                Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 21:15 +0300
                Re: Best search algorithm to find condition within a range Rustom Mody <rustompmody@gmail.com> - 2015-04-10 09:39 -0700
                Re: Best search algorithm to find condition within a range Marko Rauhamaa <marko@pacujo.net> - 2015-04-09 16:28 +0300

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