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Re: Anyone ever used vector<bool> ?

From "Alf P. Steinbach" <alf.p.steinbach@gmail.com>
Newsgroups comp.lang.c++
Subject Re: Anyone ever used vector<bool> ?
Date 2022-05-07 12:33 +0200
Organization A noiseless patient Spider
Message-ID <t55hub$f9f$1@dont-email.me> (permalink)
References (11 earlier) <87sfpn7wz2.fsf@bsb.me.uk> <t534c8$c7b$1@dont-email.me> <t53lh5$rv8$1@dont-email.me> <t53vrg$fvm$1@dont-email.me> <t55bbv$1vbf$1@gioia.aioe.org>

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On 7 May 2022 10:41, Muttley@dastardlyhq.com wrote:
> On Fri, 6 May 2022 22:18:52 +0200
> "Alf P. Steinbach" <alf.p.steinbach@gmail.com> wrote:
>> On 6 May 2022 19:22, Andrey Tarasevich wrote:
>>> If the objective were to keep `splice()` efficient, then removing
>>> inefficient `size()` from `std::list<>` entirely and forcing the user to
>>> use `std::distance` would have been an ideal solution. Beautiful idea!
>>
>> No no no. A `std::list` with O(1) other list splice can in most cases of
>> ordinary usage know its size, and it can keep track of whether it knows
> 
> Why wouldn't it always know its size? Or are you suggesting it can occasionally
> insert and delete without updating its element count?

With O(1) splice it doesn't know how many nodes are inserted unless it's 
told, and two of the splice overload don't tell it.

These are the two overloads numbered (3) in the cppreference list at
<url: https://en.cppreference.com/w/cpp/container/list/splice>.

One practical design for that case is, as I see it, to just mark the 
count as unknown, e.g. set an `optional<Size>` to empty. Then when 
`.size()` is called, do an O(n) count and cache that. Next call of 
`.size()` then has efficient O(1), and this is simple to relate to for 
programmers, but not so for academic who wants a clear single O(what?).

One way to instead force inefficiency on the client code is ¹the C++11 
design where `.size()` is required to be O(1), so that those two splice 
overloads have to count the nodes, every time. This is inefficient but 
affords a simple description in the standard. O(1) here, O(n) there.

And since efficient O(1) splice was about the only advantage of 
`std::list` over other containers such as `std::vector`, that silly C11 
decision removed the ~only advantage and made `std::list` dead meat, 
much like `std::valarray` which was a not ungood idea once.


Cheers,

- Alf

Notes:
¹ In C++98 and C++03 the standard expressed an intent of O(1) `.size()` 
via a note, "Note A" in the table of general container requirements, but 
notes in ISO standard are non-normative text.

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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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