220 5853 <7424D479-A80A-4831-93CF-AD9166C0BC63@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: Mon, 26 Aug 2013 20:09:45 -0400
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On Aug 26, 2013, at 7:57 PM, Zhihao Yuan <zy@miator.net> wrote:

> On Mon, Aug 26, 2013 at 7:22 PM, Howard Hinnant
> <howard.hinnant@gmail.com> wrote:
>> Question for Zhihao:
>> 
>> Why does forward iterator's operator*() have to return a value_type& ?
>> 
>> I'm well aware that this is what C++98/03/11 requires.  That's not what I'm asking.  I'm asking what is the benefit of this requirement in the C++1y context?  What problem does this requirement solve?
> 
> Afaics, it makes the pointed object modifiable.

But today, I can do:

std::vector<boo> v(1);
*v.begin() = true;

And yet vector<bool>::iterator::operator*() isn't returning a bool&.  But I am still modifying the referenced object.

>  And move_iterator
> significantly benefits from it.  (Here is something I'm not sure:
> move_iterator requires only InputIterator, while dereferencing an
> InputIterator may return anything convertible to T -- is there anything
> broken here?)

Yes.

http://cplusplus.github.io/LWG/lwg-active.html#2106

Howard

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