220 4679 <FF769E17-643C-47FE-8A3E-D28436A4B9A6@gmail.com> article
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From: Howard Hinnant <howard.hinnant@gmail.com>
Newsgroups: gmane.comp.lang.c++.isocpp.proposals
Subject: Re: Remove vector<bool>?
Date: Tue, 28 May 2013 16:12:21 -0400
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On May 28, 2013, at 4:00 PM, Nicol Bolas <jmckesson@gmail.com> wrote:

> Personally, I agree with Howard; we should add a class that has all of th=
is functionality (presumably with some degree of required sizing) that woul=
d be a drop-in replacement for those who need the sizing features of vector=
<bool>. But the question remains: even with a drop-in replacement, how much=
 code will be broken because of this?

Model this after the auto_ptr -> unique_ptr transition:

Step 1:  Introduce bit_vector (or whatever) and deprecate the vector<bool> =
specialization.  /Somehow/ motivate people to migrate.

Step 2:  Not to be done for at least 5-10 years after Step 1, remove the ve=
ctor<bool> specialization.

> how much code will be broken because of this?

After Step 1, none.

After Step 2, as much code as there is that:

   A.  Failed to migrate during the lengthy period that vector<bool> is dep=
recated, and
   B.  As much code that actually cares that vector<bool> was specialized.

Hopefully, little code will be broken.  While I wouldn't dream of removing =
auto_ptr today, I have the impression that the auto_ptr -> unique_ptr migra=
tion is going well, thanks to the added sweetener unique_ptr has.  Removing=
 auto_ptr for C++17 is a possibility.  If not then, then maybe C++2x.

Howard

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