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Re: Anyone ever used vector<bool> ?

From James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups comp.lang.c++
Subject Re: Anyone ever used vector<bool> ?
Date 2022-05-10 13:28 -0400
Organization A noiseless patient Spider
Message-ID <t5e7bb$38v$1@dont-email.me> (permalink)
References (21 earlier) <t5bced$16o3$1@gioia.aioe.org> <t5bdjm$v7i$2@dont-email.me> <t5bes1$fgp$1@gioia.aioe.org> <t5bg1j$8fj$1@dont-email.me> <t5e1tn$175o$1@gioia.aioe.org>

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On 5/10/22 11:55, Muttley@dastardlyhq.com wrote:
> On Mon, 9 May 2022 09:38:11 -0700
> Andrey Tarasevich <andreytarasevich@hotmail.com> wrote:
>> On 5/9/2022 9:18 AM, Muttley@dastardlyhq.com wrote:
...
>>> So why are certain people claiming a std::list won't always know the
>>> size
>>> of whats being inserted into it?
>>
>> I think it's been explained rather clearly already: spending O(n) to
>> "know" it is prohibitively expensive.
>>
>> That's, again, the crux of the issue: if we don't know "the size of
>> whats being inserted", we don't want to spend O(n) to calculate that
>> size.
>
> And then you end up with a container where size() returns an incorrect
> value.
> How is that a good thing?


Two options are under discussion:
size() never returns an incorrect value, it just may require O(n)
operations to give you the correct value. The advantage of this over
constant-time size() is that you only need to pay the O(n) cost if you
actually need the size. If size() never gets called, you never pay the
price. If it only gets called once for each list after a long series of
splices between lists, you only pay that cost once per list rather than
once per inter-list splice(). Whether or not this is an advantage
depends upon the number of inter-list splices vs. the number of
different lists.

Some people have suggested that inter-list splices are so rare that it
isn't worth worrying about - most splices are between different parts of
the same list, which never changes the list size.
Other people have suggested that essentially all splices are inter-list,
and that the O(N) time for inter-list splicing therefore removes the
only advantage that list has over the other container types.
I mistrust extreme statements, and suspect that the truth lies somewhere
between those two extremes. But I have no evidence to present in favor
of that suspicion.

The second option is that size() never returns an incorrect value,
because size() is not supported at all. If you need the number of
elements in the list, you call std::distance(l.begin(), l.end()). The
advantage of this approach over the previous one is that people won't
accidentally call size() in the incorrect expectation that it will be an
O(1) operation, as it is for most other containers.

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Thread

Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-03 15:16 +0000
  Re: Anyone ever used vector<bool> ? Ben <ben.usenet@bsb.me.uk> - 2022-05-03 16:39 +0100
    Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-03 16:12 +0000
      Re: Anyone ever used vector<bool> ? Bo Persson <bo@bo-persson.se> - 2022-05-03 20:25 +0200
        Re: Anyone ever used vector<bool> ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-05-03 12:00 -0700
        Re: Anyone ever used vector<bool> ? Juha Nieminen <nospam@thanks.invalid> - 2022-05-04 10:50 +0000
  Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-03 16:14 +0000
  Re: Anyone ever used vector<bool> ? Jack Lemmon <invalid@invalid.net> - 2022-05-03 17:33 +0100
    Re: Anyone ever used vector<bool> ? Manfred <noname@add.invalid> - 2022-05-03 19:13 +0200
      Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-04 09:13 +0000
    Re: Anyone ever used vector<bool> ? Juha Nieminen <nospam@thanks.invalid> - 2022-05-04 10:45 +0000
      Re: Anyone ever used vector<bool> ? Paavo Helde <eesnimi@osa.pri.ee> - 2022-05-04 14:09 +0300
        Re: Anyone ever used vector<bool> ? Frederick Virchanza Gotham <cauldwell.thomas@gmail.com> - 2022-05-04 14:39 -0700
          Re: Anyone ever used vector<bool> ? red floyd <no.spam.here@its.invalid> - 2022-05-04 15:17 -0700
            Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-05 01:57 -0400
          Re: Anyone ever used vector<bool> ? Paavo Helde <eesnimi@osa.pri.ee> - 2022-05-05 09:12 +0300
        Re: Anyone ever used vector<bool> ? Juha Nieminen <nospam@thanks.invalid> - 2022-05-05 06:17 +0000
          Re: Anyone ever used vector<bool> ? Ben <ben.usenet@bsb.me.uk> - 2022-05-05 10:49 +0100
            Re: Anyone ever used vector<bool> ? Öö Tiib <ootiib@hot.ee> - 2022-05-05 04:29 -0700
              Re: Anyone ever used vector<bool> ? Ben <ben.usenet@bsb.me.uk> - 2022-05-05 12:56 +0100
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-05 21:37 +0200
                Re: Anyone ever used vector<bool> ? Ben <ben.usenet@bsb.me.uk> - 2022-05-05 21:13 +0100
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-06 10:39 +0200
                Re: Anyone ever used vector<bool> ? Ben <ben.usenet@bsb.me.uk> - 2022-05-06 11:54 +0100
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-06 14:29 +0200
                Re: Anyone ever used vector<bool> ? Ben <ben.usenet@bsb.me.uk> - 2022-05-06 17:05 +0100
                Re: Anyone ever used vector<bool> ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-06 10:22 -0700
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-06 22:18 +0200
                Re: Anyone ever used vector<bool> ? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-05-06 13:51 -0700
                Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-07 08:41 +0000
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-07 12:33 +0200
                Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-07 16:12 +0000
                Re: Anyone ever used vector<bool> ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-07 09:37 -0700
                Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-09 09:02 +0000
                Re: Anyone ever used vector<bool> ? Bo Persson <bo@bo-persson.se> - 2022-05-09 12:14 +0200
                Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-09 15:36 +0000
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-09 11:56 -0400
                Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-09 16:18 +0000
                Re: Anyone ever used vector<bool> ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-09 09:38 -0700
                Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-10 15:55 +0000
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-10 13:28 -0400
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-10 10:16 -0400
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-10 18:40 +0200
                Re: Anyone ever used vector<bool> ? Manfred <noname@add.invalid> - 2022-05-10 19:50 +0200
                Re: Anyone ever used vector<bool> ? Öö Tiib <ootiib@hot.ee> - 2022-05-12 05:44 -0700
                Re: Anyone ever used vector<bool> ? Manfred <noname@add.invalid> - 2022-05-12 17:24 +0200
                Re: Anyone ever used vector<bool> ? Öö Tiib <ootiib@hot.ee> - 2022-05-12 20:11 -0700
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-12 12:53 -0400
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-12 22:53 -0400
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-13 18:34 +0200
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-13 23:46 -0400
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-14 11:43 +0200
                Re: Anyone ever used vector<bool> ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-05-15 07:48 -0700
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-16 03:30 +0200
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-15 22:57 -0400
                Re: Anyone ever used vector<bool> ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-05-17 05:30 -0700
                Re: Anyone ever used vector<bool> ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-05-17 05:19 -0700
                Re: Anyone ever used vector<bool> ? Juha Nieminen <nospam@thanks.invalid> - 2022-05-16 05:46 +0000
                Re: Anyone ever used vector<bool> ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-05-17 05:37 -0700
                Re: Anyone ever used vector<bool> ? wij <wyniijj2@gmail.com> - 2022-05-12 08:05 -0700
                Re: Anyone ever used vector<bool> ? scott@slp53.sl.home (Scott Lurndal) - 2022-05-09 17:20 +0000
                Re: Anyone ever used vector<bool> ? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-05-09 12:05 -0700
                Re: Anyone ever used vector<bool> ? Bo Persson <bo@bo-persson.se> - 2022-05-09 21:57 +0200
                Re: Anyone ever used vector<bool> ? wij <wyniijj2@gmail.com> - 2022-05-09 13:56 -0700
                Re: Anyone ever used vector<bool> ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-09 08:33 -0700
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-09 11:56 -0400
                Re: Anyone ever used vector<bool> ? Manfred <noname@add.invalid> - 2022-05-09 18:13 +0200
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-10 10:14 -0400
                Re: Anyone ever used vector<bool> ? scott@slp53.sl.home (Scott Lurndal) - 2022-05-10 14:31 +0000
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-07 18:38 +0200
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-07 18:28 -0400
                Re: Anyone ever used vector<bool> ? Manfred <noname@add.invalid> - 2022-05-08 18:37 +0200
                Re: Anyone ever used vector<bool> ? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-05-08 11:50 -0700
                Re: Anyone ever used vector<bool> ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-05-08 18:18 -0400
                Re: Anyone ever used vector<bool> ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-07 09:45 -0700
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-07 19:12 +0200
                Re: Anyone ever used vector<bool> ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-07 20:36 -0700
                Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-08 08:26 +0200
                Re: Anyone ever used vector<bool> ? scott@slp53.sl.home (Scott Lurndal) - 2022-05-06 13:55 +0000
                Re: Anyone ever used vector<bool> ? Juha Nieminen <nospam@thanks.invalid> - 2022-05-06 06:35 +0000
                Re: Anyone ever used vector<bool> ? Ben <ben.usenet@bsb.me.uk> - 2022-05-06 11:29 +0100
                Re: Anyone ever used vector<bool> ? Juha Nieminen <nospam@thanks.invalid> - 2022-05-09 04:58 +0000
                Re: Anyone ever used vector<bool> ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-08 22:30 -0700
  Re: Anyone ever used vector<bool> ? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-05-03 14:41 -0700
  Re: Anyone ever used vector<bool> ? Andrea Venturoli <ml.diespammer@netfence.it> - 2022-05-04 08:20 +0200
  Re: Anyone ever used vector<bool> ? wij wij <wyniijj2@gmail.com> - 2022-05-04 03:21 -0700
    Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-04 10:52 +0000
  Re: Anyone ever used vector<bool> ? Juha Nieminen <nospam@thanks.invalid> - 2022-05-04 10:47 +0000
    Re: Anyone ever used vector<bool> ? Muttley@dastardlyhq.com - 2022-05-04 10:53 +0000
  Re: Anyone ever used vector<bool> ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-06-01 05:46 +0200
    Re: Anyone ever used vector<bool> ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-06-01 07:31 +0200
    Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-06-01 14:20 +0200
      Re: Anyone ever used vector<bool> ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-06-01 14:23 +0200
        Re: Anyone ever used vector<bool> ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-06-01 14:26 +0200
          Re: Anyone ever used vector<bool> ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-06-01 14:40 +0200

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