Re: [boost] [sandbox][move] Regular requirement

From: Michael Marcin (mike.marcin_at_[hidden])
Date: 2008-07-31 16:27:40

Daniel James wrote:
> 2008/7/31 Michael Marcin <mike.marcin_at_[hidden]>:
> 
>> However the documentation says that objects have to model the Regular
>> concept in order to model the Movable concept. This seems unfortunate as
>>  Regular puts a lot of requirements on types that don't seem necessary to
>> gain moving. It requires Assignable which requires a copy constructor and it
>> requires EqualityComparable which seems unnecessary.
> 
> Sorry, the documentation is out of date, I haven't updated it for the
> changes I've made. The library does supports noncopyable types. If you
> can decipher it there is an example in the unit tests (in y.hpp - I'll
> probably rename that file). You have to implement it a little
> differently to your normal noncopyable type. The signature is
> something like:

Fantastic. I sort of figured it does since I'm using them just wanted to 
make sure it was a feature and not a bug.

> 
> class noncopyable
> {
>    // Private constructor to make it noncopyable.
>    // Note that it's a non-const reference
>    noncopyable(noncopyable&);
> public:
>    noncopyable();
>    ~noncopyable();
>    noncopyable(boost::move_from<noncopyable>); // Move constructor
>    noncopyable& operator=(noncopyable); // Move assignment
>    operator boost::move_from<noncopyable>() {
>        return boost::move_from<noncopyable>(*const_cast<noncopyable*>(this));
>    }
> };

The implicit conversion to move_from seems very dangerous to me.

> 
> I should warn you that the library will probably change to support
> other types and hopefully rvalue references. I'll be resuming work on
> it soon after this release is done.
> 

I'm looking forward to it.

Thanks,

Michael Marcin