Re: [boost] [container] Issues with non-copyable mapped-types

Subject: Re: [boost] [container] Issues with non-copyable mapped-types
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2011-09-15 16:46:44

El 15/09/2011 21:12, Jeffrey Lee Hellrung, Jr. escribió:
> On Thu, Sep 15, 2011 at 12:21 AM, onlyone_at_[hidden]<onlyone_at_[hidden]
>> wrote:
>
>> Hi,
>>
>> I have been trying to use Boost.Container to make a
>> map<copyable_but_not_moveable, moveable_but_not_copyable>.
>>
>> Unfortunately I have been unable to do this because the value_type of
>> boost::container::map is std::pair, which does not support move semantics
>> (in C++03). This causes problems for the moveable_but_not_copyable type. It
>> means that, for example:
>>
>>     myMap[copyable_but_not_moveable()];
>>
>> does not compile. This behaviour is fully supported in C++11 mode, and I
>> see no reason why a custom C++03 pair class would be unable to use the
>> Boost.Move emulation to achieve the same effect.
>>
>
> I assume Boost.Container does not provide its own C++03 move-emulation pair
> class, does it?  In which case, probably the fastest way to get such a pair
> class into Boost.Container is to provide a patch with an implementation.
> And, yes, I agree that this is a desirable and useful addition.

It has some internal pair class that is reinterpret_cast-ed (alarm!) to 
std::pair (map requires std::pair, there's no choice). I think it is not 
a fully drop-in replacement for std::pair (e.g., piecewise_construct) 
but I think it can be a good start.

Best,

Ion