Re: [boost] C++03 unique_ptr emulation

Subject: Re: [boost] C++03 unique_ptr emulation
From: David Abrahams (dave_at_[hidden])
Date: 2009-01-09 15:29:46

on Fri Jan 09 2009, Ion Gaztañaga <igaztanaga-AT-gmail.com> wrote:

> David Abrahams wrote:
>> So you're saying, in other words, that "move(x)" really means "you have
>> permission to move x" but the one I proposed would mean "move it, now."
>>
>> OK, good point.
>>
>> So what about this horrible little proposal?
>>
>>   template <class T>
>>   struct rv<T> : T
>>   {
>>    private:
>>       rv();
>>       ~rv();
>>       rv(rv const&);
>>       void operator=(rv const&);
>>   };
>>
>>   template <class T>
>>   boost::enable_if<is_class<T>, rv<T>&>
>>   move(T& x)
>>   {
>>     return static_cast<rv<T>& >(x);
>>   }
>>
>> Does that solve any problems?
>
> How can that work? What would you need to add to T? Disable non-const
> copy constructor?

Well, I haven't thought this through deeply (nor really tested
anything), but the idea is that movable types would have a stealing
conversion from rv<T>& but non-movable types should just use the copy
ctor that slices off the non-existent derived class.

>> Yeah, I know it's not theoretically portable, but it should be portable
>> in practice.  Especially when it comes to emulating language features, I
>> care less and less about the letter of the law :-)
>
> I would be really interested in this proposal.

I'm not even sure if it addresses the problems you're working on, but
it's a thought.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com