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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c++
Subject: Re: Anyone ever used vector<bool> ?
Date: Sun, 15 May 2022 07:48:07 -0700
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"Alf P. Steinbach" <alf.p.steinbach@gmail.com> writes:

> On 14 May 2022 05:46, James Kuyper wrote:
>
>> On 5/13/22 12:34, Alf P. Steinbach wrote:
>>
>>> On 13 May 2022 04:53, James Kuyper wrote:
>>
>> ...
>>
>>>> [Correction to my previous post, which I've cancelled - but cancellation
>>>> requests are usually ignored]
>>>> That's covered by the second option.  Just because the specification
>>>> allows
>>>> size() to be O(N) doesn't meant that it's required to always involve
>>>> O(N) operations.
>>>
>>> By that logic it can be described as O(n^2 ).
>>
>> You misunderstand.  This isn't a description.
>>
>>> And it's within the formal definition of big O notation.
>>>
>>> However, using it that way would be very misleading so it's not done;
>>> there is an understanding that the big O communicates something useful
>>> to know, whereas the way you used it it communicated a falsehood.
>>
>> Since it's not a description, it can't be a false description, either.
>> It's a specification.  Standard specifications can neither be false, nor
>> true.  A given implementation either meets the specifications, or it
>> doesn't.  The specifications might be impossible to meet, but that's a
>> different matter entirely from truth or falsity.
>>
>> Whenever the standard specifies the complexity of an operation, an
>> implementation that has a lower complexity is always allowed.  In
>> particular, if the standard specifies O(N), an implementation that
>> sometimes takes O(1) time, and sometimes takes O(N) meets that
>> specification.  An implementation that took O(N^2) time would not.
>
> That's a meaningless response.

James's response is not meaningless.  It is a bit sloppy in
places in how it uses big-O notation, but it is not meaningless.
If you have trouble understanding what he means I suggest asking
a question.

> I guess by design.

It's hard to see this comment as anything but a gratuitous
insult.  Heaven know I don't always agree with what James has to
say, but he is not someone given to making statements that are
deliberately meaningless, and I certainly believe he did not
do so in this instance.