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Re: This code is effective for modest-sized numbers, but can you tell what it does?

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Öö Tiib <ootiib@hot.ee> wrote:
> On Monday, 25 April 2022 at 15:27:42 UTC+3, Tim Rentsch wrote:
>> Juha Nieminen <nos...@thanks.invalid> writes: 
>> 
>> > Graeme C. <gra...@gmail.com> wrote: 
>> 
>> [...]
>> >> for (int i=0; i<vf[gen-1].size(); i++) { // from previous gen 
>> > 
>> > std::vector::size() returns a value of type std::size_t. You 
>> > shouldn't be using an int with it.
>> I don't want to start a holy war, but in this particular case 
>> there is no problem comparing a signed type to a size_t (which is 
>> an unsigned type). More generally, whenever a value of a signed 
>> type has a non-negative value, as is obviously true in this 
>> construct, then there is never a problem comparing a value of a 
>> signed type to a value of an unsigned type. 
>> 
>> Some people prefer using an unsigned type for indexing variables 
>> like 'i' above, and that a reasonable style choice here IMO. But 
>> there is nothing logically wrong with giving 'i' a signed type 
>> here instead.
> 
> The issue as I read it was about chance that int is 32 bits, the 
> vf[gen-1] has 2,200,000,000 elements and so the ++ will be 
> applied to INT_MAX  that is undefined behavior.

Yeah, it's not that much about the signedness, but about the size.
After all, the program accepts a 'long long' value as input, so
ostensibly the vector might have more than INT_MAX and even more
than UINT_MAX elements (might not be the case with this particular
program, I haven't checked, but in general it could be).

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This code is effective for modest-sized numbers, but can you tell what it does? "Graeme C." <graec58@gmail.com> - 2022-04-22 04:41 -0700
  Re: This code is effective for modest-sized numbers, but can you tell what it does? Christian Gollwitzer <auriocus@gmx.de> - 2022-04-22 17:19 +0200
    Re: This code is effective for modest-sized numbers, but can you tell what it does? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-04-22 17:42 +0200
      Re: This code is effective for modest-sized numbers, but can you tell what it does? red floyd <no.spam.here@its.invalid> - 2022-04-22 09:16 -0700
  Re: This code is effective for modest-sized numbers, but can you tell what it does? Frederick Gotham <cauldwell.thomas@gmail.com> - 2022-04-22 09:22 -0700
    Re: This code is effective for modest-sized numbers, but can you tell what it does? "Graeme C." <graec58@gmail.com> - 2022-04-22 10:24 -0700
      Re: This code is effective for modest-sized numbers, but can you tell what it does? Christian Gollwitzer <auriocus@gmx.de> - 2022-04-22 20:33 +0200
        Re: This code is effective for modest-sized numbers, but can you tell what it does? "Graeme C." <graec58@gmail.com> - 2022-04-22 17:57 -0700
  Re: This code is effective for modest-sized numbers, but can you tell what it does? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-22 19:18 -0700
    Re: This code is effective for modest-sized numbers, but can you tell what it does? "Graeme C." <graec58@gmail.com> - 2022-04-22 19:40 -0700
      Re: This code is effective for modest-sized numbers, but can you tell what it does? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-22 20:00 -0700
        Re: This code is effective for modest-sized numbers, but can you tell what it does? "Graeme C." <graec58@gmail.com> - 2022-04-23 04:21 -0700
  Re: This code is effective for modest-sized numbers, but can you tell what it does? Juha Nieminen <nospam@thanks.invalid> - 2022-04-25 05:48 +0000
    Re: This code is effective for modest-sized numbers, but can you tell what it does? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-25 05:27 -0700
      Re: This code is effective for modest-sized numbers, but can you tell what it does? Öö Tiib <ootiib@hot.ee> - 2022-04-25 05:40 -0700
        Re: This code is effective for modest-sized numbers, but can you tell what it does? Vir Campestris <vir.campestris@invalid.invalid> - 2022-04-25 16:48 +0100
          Re: This code is effective for modest-sized numbers, but can you tell what it does? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-30 03:51 -0700
            Re: This code is effective for modest-sized numbers, but can you tell what it does? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-30 08:28 -0700
              Re: This code is effective for modest-sized numbers, but can you tell what it does? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-30 10:30 -0700
              Re: This code is effective for modest-sized numbers, but can you tell what it does? Manfred <noname@add.invalid> - 2022-04-30 19:20 +0200
                Re: This code is effective for modest-sized numbers, but can you tell what it does? Manfred <noname@add.invalid> - 2022-04-30 23:20 +0200
                Re: This code is effective for modest-sized numbers, but can you tell what it does? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-30 10:40 -0700
              Re: This code is effective for modest-sized numbers, but can you tell what it does? Manfred <noname@add.invalid> - 2022-04-30 19:12 +0200
        Re: This code is effective for modest-sized numbers, but can you tell what it does? Juha Nieminen <nospam@thanks.invalid> - 2022-04-26 05:20 +0000
          Re: This code is effective for modest-sized numbers, but can you tell what it does? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-29 16:12 -0700
      Re: This code is effective for modest-sized numbers, but can you tell what it does? Paavo Helde <eesnimi@osa.pri.ee> - 2022-04-25 15:44 +0300
        Re: This code is effective for modest-sized numbers, but can you tell what it does? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-05-10 07:18 -0700
          Re: This code is effective for modest-sized numbers, but can you tell what it does? scott@slp53.sl.home (Scott Lurndal) - 2022-05-10 14:34 +0000
            Re: This code is effective for modest-sized numbers, but can you tell what it does? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-05-24 05:43 -0700
          Re: This code is effective for modest-sized numbers, but can you tell what it does? Paavo Helde <eesnimi@osa.pri.ee> - 2022-05-10 20:34 +0300
            Re: This code is effective for modest-sized numbers, but can you tell what it does? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-06-04 07:57 -0700

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