220 4713 <a077c61e-bf59-4d4d-8aa4-b6a810e47595@isocpp.org> article
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From: Nicol Bolas <jmckesson@gmail.com>
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Subject: Re: Remove vector<bool>?
Date: Wed, 29 May 2013 12:21:25 -0700 (PDT)
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On Wednesday, May 29, 2013 10:51:42 AM UTC-7, Nevin ":-)" Liber wrote:
>
> On 29 May 2013 12:42, Nicol Bolas <jmck...@gmail.com <javascript:>> wrote:
>
>>
>>   http://www.gotw.ca/publications/N1185.pdf 
>>>
>>> But it's not adopted. 
>>>
>>> Anyway, vector<bool> sucks, and we know it.  How about to entirely 
>>> remove it? 
>>>
>>
>>
>>
>> We simply add another specialization to `vector` called 
>> "vector<std::real_bool, Allocator>". If you create a `vector` with the 
>> `std::real_bool` type, then you get exactly what you would have gotten if 
>> `vector<bool>` weren't a specialization: an actual `vector` that contains 
>> actual `bool`s. The `value_type` of `vector<std::real_bool>` would be 
>> `bool`, and so forth.
>>
>> We don't have to get rid of `vector<bool>` to get what we want. We just 
>> have to call it something else. And since this `std::real_bool` type can't 
>> be used in existing code (defining new things in the `std` namespace is 
>> undefined behavior), it can't conflict with anything now.
>>
>> The downside is that a template function that takes a `vector<T>`, where 
>> `T` is some type, may assume that `T` is the `value_type` of the `vector`, 
>> which it would not be in the case of `std::real_bool`.
>>
>
> -1.
>
> The primary argument (so far) for removing the vector<bool> specialization 
> is uniformity with the rest of vector.
>

I thought the primary argument was to be able to create a `vector` of 
`bool`s. I don't care about "uniformity"; what I care about is making a 
`vector` that actually contains `bool`s.

As you point out, your solution still doesn't achieve it.
>
> While the standard strives for high levels of backwards compatibility, it 
> need not be 100% (heck, C++11 vector is not 100% backwards compatible with 
> C++03 vector), and we shouldn't be adding more warts.  The standard is the 
> right place to fix this, and we should fix it and not just put a band aid 
> on it.
>

And how long will that take? C++14 is closed for new stuff, and the whole 
"deprecation/removal" process will require at least 2 revisions. So it 
would be C++20 *at least* before we can finally create a real `vector` of 
real `bool`s.

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On Wednesday, May 29, 2013 10:51:42 AM UTC-7, Nevin ":-)" Liber wrote:<bloc=
kquote class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-l=
eft: 1px #ccc solid;padding-left: 1ex;">On 29 May 2013 12:42, Nicol Bolas <=
span dir=3D"ltr">&lt;<a href=3D"javascript:" target=3D"_blank" gdf-obfuscat=
ed-mailto=3D"kVPNKppxaKIJ">jmck...@gmail.com</a>&gt;</span> wrote:<br><div =
class=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=3D"margin:0 0=
 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">

<div><br><blockquote class=3D"gmail_quote" style=3D"margin:0;margin-left:0.=
8ex;border-left:1px #ccc solid;padding-left:1ex">&nbsp; <a href=3D"http://w=
ww.gotw.ca/publications/N1185.pdf" target=3D"_blank">http://www.gotw.ca/<wb=
r>publications/N1185.pdf</a>
<br>
<br>But it's not adopted.
<br>
<br>Anyway, vector&lt;bool&gt; sucks, and we know it. &nbsp;How about to en=
tirely
<br>remove it?
<br></blockquote></div><div><br><br><br>We simply add another specializatio=
n to `vector` called "vector&lt;std::real_bool, Allocator&gt;". If you crea=
te a `vector` with the `std::real_bool` type, then you get exactly what you=
 would have gotten if `vector&lt;bool&gt;` weren't a specialization: an act=
ual `vector` that contains actual `bool`s. The `value_type` of `vector&lt;s=
td::real_bool&gt;` would be `bool`, and so forth.<br>

<br>We don't have to get rid of `vector&lt;bool&gt;` to get what we want. W=
e just have to call it something else. And since this `std::real_bool` type=
 can't be used in existing code (defining new things in the `std` namespace=
 is undefined behavior), it can't conflict with anything now.<br>

<br>The downside is that a template function that takes a `vector&lt;T&gt;`=
, where `T` is some type, may assume that `T` is the `value_type` of the `v=
ector`, which it would not be in the case of `std::real_bool`.<br></div>

</blockquote><div><br>-1.<br><br>The primary argument (so far) for removing=
 the vector&lt;bool&gt; specialization is uniformity with the rest of vecto=
r.</div></div></blockquote><div><br>I thought the primary argument was to b=
e able to create a `vector` of `bool`s. I don't care about "uniformity"; wh=
at I care about is making a `vector` that actually contains `bool`s.<br><br=
></div><blockquote class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.=
8ex;border-left: 1px #ccc solid;padding-left: 1ex;"><div class=3D"gmail_quo=
te"><div>As you point out, your solution still doesn't achieve it.<br><br>

While the standard strives for high levels of backwards compatibility, it n=
eed not be 100% (heck, C++11 vector is not 100% backwards compatible with C=
++03 vector), and we shouldn't be adding more warts.&nbsp; The standard is =
the right place to fix this, and we should fix it and not just put a band a=
id on it.</div></div></blockquote><div><br>And how long will that take? C++=
14 is closed for new stuff, and the whole "deprecation/removal" process wil=
l require at least 2 revisions. So it would be C++20 <i>at least</i> before=
 we can finally create a real `vector` of real `bool`s.<br></div>

<p></p>

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&nbsp;<br />
&nbsp;<br />

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